ohm's law case study

Current Electricity

Ohm’s law states the relationship between electric current and potential difference. The current that flows through most conductors is directly proportional to the voltage applied to it. Georg Simon Ohm, a German physicist was the first to verify Ohm’s law experimentally.

Ohm’s Law Explanation

One of the most basic and important laws of electric circuits is Ohm’s law.

Ohm’s law states that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperatures remain constant.

Mathematically, this current-voltage relationship is written as,

In the equation, the constant of proportionality, R, is called Resistance and has units of ohms, with the symbol Ω.

The same formula can be rewritten in order to calculate the current and resistance respectively as follows:

Ohm’s law only holds true if the provided temperature and the other physical factors remain constant. In certain components, increasing the current raises the temperature . An example of this is the filament of a light bulb, in which the temperature rises as the current is increased. In this case, Ohm’s law cannot be applied. The lightbulb filament violates Ohm’s Law .

: Ohm’s law states that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperature, remain constant.

: V = IR, where V is the voltage across the conductor, I is the current flowing through the conductor and R is the resistance provided by the conductor to the flow of current.

Relationship Between Voltage, Current and Resistance

Water Pipe Analogy for Ohm’s Law

Ohm’s Law describes the current flow through a resistance when different electric potentials (voltage) are applied at each end of the resistance . Since we can’t see electrons, the water-pipe analogy helps us understand the electric circuits better. Water flowing through pipes is a good mechanical system that is analogous to an electrical circuit.

Here, the voltage is analogous to water pressure, the current is the amount of water flowing through the pipe, and the resistance is the size of the pipe. More water will flow through the pipe (current) when more pressure is applied (voltage) and the bigger the pipe (lower the resistance).

The video below shows the physical demonstration of the Waterpipe analogy and explains to you the factors that affect the flow of current

Experimental Verification of Ohm’s Law

Ohm’s Law can be easily verified by the following experiment:

Apparatus Required:

Initially, the key K is closed and the rheostat is adjusted to get the minimum reading in ammeter A and voltmeter V.
The current in the circuit is increased gradually by moving the sliding terminal of the rheostat. During the process, the current flowing in the circuit and the corresponding value of potential difference across the resistance wire R are recorded.
This way different sets of values of voltage and current are obtained.
For each set of values of V and I, the ratio of V/I is calculated.
When you calculate the ratio V/I for each case, you will come to notice that it is almost the same. So V/I = R, which is a constant.
Plot a graph of the current against the potential difference, it will be a straight line. This shows that the current is proportional to the potential difference.

Ohm’s Law Magic Triangle

Ohm’s Law Solved Problems

Example 1: If the resistance of an electric iron is 50 Ω and a current of 3.2 A flows through the resistance. Find the voltage between two points.

If we are asked to calculate the value of voltage with the value of current and resistance, then cover V in the triangle. Now, we are left with I and R or more precisely I × R.

Therefore, we use the following formula to calculate the value of V:

Substituting the values in the equation, we get

V = 3.2 A × 50 Ω = 160 V

Example 2: An EMF source of 8.0 V is connected to a purely resistive electrical appliance (a light bulb). An electric current of 2.0 A flows through it. Consider the conducting wires to be resistance-free. Calculate the resistance offered by the electrical appliance.

When we are asked to determine the value of resistance when the values of voltage and current are given, we cover R in the triangle. This leaves us with only V and I, more precisely V ÷ I.

R = 8 V ÷ 2 A = 4 Ω

Calculating Electrical Power Using Ohm’s Law

The rate at which energy is converted from the electrical energy of the moving charges to some other form of energy like mechanical energy, heat energy, energy stored in magnetic fields or electric fields, is known as electric power. The unit of power is the watt. The electrical power can be calculated using Ohm’s law and by substituting the values of voltage, current and resistance.

Formula to find power

What is a Power Triangle?

The power triangle can be employed to determine the value of electric power, voltage and current when the values of the other two parameters are given to us. In the power triangle, the power (P) is on the top and current (I) and voltage (V) are at the bottom.

Ohm’s Law Pie Chart

Ohm’s Law Matrix Table

Ohm’s Law Applications

The main applications of Ohm’s law are:

To determine the voltage, resistance or current of an electric circuit.
Ohm’s law maintains the desired voltage drop across the electronic components.
Ohm’s law is also used in DC ammeter and other DC shunts to divert the current.

Limitations of Ohm’s Law

Following are the limitations of Ohm’s law:

Ohm’s law is not applicable for unilateral electrical elements like diodes and transistors as they allow the current to flow through in one direction only.
For non-linear electrical elements with parameters like capacitance, resistance etc the ratio ofvoltage and current won’t be constant with respect to time making it difficult to use Ohm’s law.

The video about conductance, resistance, and ohm’s law

Frequently Asked Questions – FAQs

What does ohm’s law state.

Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

What can Ohm’s law be used for?

Ohm’s law is used to validate the static values of circuit components such as current levels, voltage supplies, and voltage drops.

Is Ohm’s law Universal?

No. Ohm’s law is not a universal law. This is because Ohm’s law is only applicable to ohmic conductors such as iron and copper but is not applicable to non-ohmic conductors such as semiconductors.

Why is Ohm’s law not applicable to semiconductors?

Ohm’s law doesn’t apply to semiconducting devices because they are nonlinear devices. This means that the ratio of voltage to current doesn’t remain constant for variations in voltage.

When does Ohm’s law fail?

Ohm’s law fails to explain the behaviour of semiconductors and unilateral devices such as diodes. Ohm’s law may not give the desired results if the physical conditions such as temperature or pressure are not kept constant.

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Electricity of Class 10

The flow of electric current through a conductor depends on the potential difference across its ends. At a particular temperature, the strength of current flowing through it is directly proportional to the potential difference across its ends. This is known as Ohm's Law.

or V ∝ I V = Potential difference

V = RI R = Resistance

or R = V/I, I = Current

Here, R is the constant of proportionality, which depends on size, nature of material and temperature. R is called the electrical resistance or resistance of the conductor.

EXPERIMENTAL VERIFICATION OF OHM'S LAW

Set up a circuit as shown in figure consisting of a nichrome wire XY of length, say 0.5 m, an ammeter, a voltmeter and four cells of 1.5 V each. (Nichrome is an alloy of nickel, chromium, manganese, and iron metal.)
First use only one cell as the source in the circuit. Note the reading in the ammeter I, for the current and reading of the voltmeter V for the potential difference across the nichrome wire XY in the circuit. Tabulate them.
Next connect two cells in the circuit and note the respective readings of the ammeter and voltmeter for the values of current through the nichrome wire and potential difference across the nichrome wire.

Repeat the above steps using three cells and then four cells in the circuit separately.
Calculate the ratio of V to I for each pair of potential difference (V) and current (I).
Plot a graph between V and I, and observe the nature of the graph.

Thus, V/I is a constant ratio which is called resistance (R). It is known as Ohm’s Law.

RESISTANCE OF A CONDUCTOR:

The electric current is a flow of electrons through a conductor. When the electrons move from one part of the conductor to the other part, they collide with other electrons and with the atoms and ions present in the body of the conductor. Due to these collisions, there is some obstruction or opposition to the flow of electrons through the conductor.

The property of a conductor due to which it opposes the flow of current through it, is called resistance. The resistance of a conductor is numerically equal to the ratio of potential difference across its ends to the current flowing through it.

Resistance = Potential difference/Current, Or R = V/I

UNIT OF RESISTANCE

The S.I. unit of resistance is Ohm (Ω)

1 Ohm (Ω) = 1 volt(1V)/ Ampere(1 A)

The resistance of a conductor is said to be one ohm if a current of one ampere flows through it when a potential difference of one volt is applied across its ends.

CONDUCTORS, RESISTORS AND INSULATORS:

On the basis of their electrical resistance, all the substances can be divided into three groups:

conductors, resistors and insulators.

Conductors:

Those substances which have very low electrical resistance are called conductors. A conductor allows the electricity to flow through it easily. Silver metal is the best conductor of electricity Copper and Aluminium metals are also good conductors. Electric wires are made of Copper or Aluminium because they have very low electrical resistance.

Those substances which have comparatively high electrical resistance, are called resistors. The alloys like nichrome, manganin and constantan (or ureka), all have quite high resistances, so they are used to make those electrical devices where high resistance is required. A resistor reduces the current in the circuit.

Insulators:

Those substances which have infinitely high electrical resistance are called insulators. An insulator does not allow electricity to flow through it. Rubber is an excellent insulator. Electricians wear rubber handgloves while working with electricity because rubber is an insulator and protects them from electric shocks. Wood is also a good insulator.

CAUSE OF RESISTANCE:

There are many free electrons in a conductor. They move randomly when no electric current is passing through it. But when current is passed through it, they being negatively charged, start moving towards positive end of conductor, with a velocity called Drift velocity. During this movement, they collide with atoms, or ions of the conductor and thus their velocity is slowed down. This slow down due to obstruction is called Resistance.

Activity to show that the amount of current through an electric component depends upon its resistance:

Take a nichrome wire, a torch bulb, a 10 W bulb and an ammeter (0-5 A range), a plug key and some connecting wires.
Set up the circuit by connecting four dry cells of 1.5 V each in series with the ammeter leaving a gap XY in the circuit, as shown in figure.

Complete the circuit by connecting the nichrome wire in the gap XY. Plug the key. Note down the ammeter reading. Take out the key from the plug. [Note: Always take out the key from the plug after measuring the current through the circuit.]
Replace the nichrome wire with the torch bulb in the circuit and find the current through it by measuring the reading of the ammeter.
Now repeat the above step with 10 W bulb in the gap XY.
You will notice that the ammeter readings differ for different components connected in the gap XY.
You may repeat this Activity by keeping any material component in the gap. Observe the ammeter readings in each case. Analyse the observations.

Thus, we come to a conclusion that current through an electric component depends upon its resistance.

FACTORS AFFECTING RESISTANCE OF A CONDUCTOR

Resistance depends upon the following factors:-

(i) Length of the conductor.

(ii) Area of cross-section of the conductor (or thickness of the conductor).

(iii) Nature of the material of the conductor.

(iv) Temperature of the conductor.

Mathematically: It has been found by experiments that:

(i) The resistance of a given conductor is directly proportional to its length i.e.

R ∝ l ….(i)

(ii) The resistance of a given conductor is inversely proportional to its area of cross-section i.e.

R ∝ 1/A ….(ii)

From (i) and (ii), R ∝ 1/A

R = ρ x 1/A…(iii)

Where ρ (rho) is a constant known as resistivity of the material of the conductor. Resistivity is also known as specific resistance.

DEPENDANCY OF RESISTANCE ON TEMPERATURE:

If R 0 is the resistance of the conductor at 0°C and R1 is the resistance of the conductor at t°C then the relation between R0 and R1 is given by,

R 1 = R o (1 + θαΔt) [Here Δt = t – 0 = t]

Here, a = Coefficient of Resistivity, t = temperature in °C

Experiment to show that resistance of a conductor depends on its length, cross section area and nature of its material.

Complete an electric circuit consisting of a cell, an ammeter, a nichrome wire of length [marked (1)] and a plug key, as shown in figure.
Now, plug the key. Note the current in the ammeter.

Replace the nichrome wire by another nichrome wire of same thickness but twice the length, that is 2 [marked (2) in the figure].
Note the ammeter reading.
Now replace the wire by a thicker nichrome wire, of the same length [marked(3)]. A thicker wire has a larger cross-sectional area. Again note down the current through the circuit.
Instead of taking a nichrome wire, connect a copper wire [marked (4) in figure] in the circuit. Let the wire be of the same length and same area of cross-section as that of the first nichrome wire [marked(1)]. Note the value of the current.
Notice the difference in the current in all cases.
We notice that the current depends on the length of the conductor.
We also observed that the current depends on the area of cross-section of the wire used.

RESISTIVITY:

Resistivity, ρ = R x A/1….(iv)

By using this formula, we will now obtain the definition of resistivity. Let us take a conductor having a unit area of cross-section of 1 m 2 and a unit length of 1 m. So, putting A= 1 and l = 1 in equation (iv),

Resistivity, ρ = R

The resistivity of a substance is numerically equal to the resistance of a rod of that substance which is 1 metre long and 1 metre square in cross-section.

Unit of resistivity,

The S.I. unit of resistivity is ohm-metre which is written in symbols as Ω - m.

Resistivity of a substance does not depend on its length or thickness. It depends only on the nature of the substance. The resistivity of a substance is its characteristic property. So, we can use the resistivity values to compare the resistances of two or more substances.

Importance of resistivity:

A good conductor of electricity should have a low resistivity and a poor conductor of electricity should have a high resistivity. The resistivities of alloys are much more higher than those of the pure metals. It is due to their high resistivities that manganin and constantan alloys are used to make resistance wires used in electronic appliances to reduce the current in an electrical circuit.

Nichrome alloy is used for making the heating elements of electrical appliances like electric irons, room-heaters, water-heaters and toasters etc. because it has very high resistivity and it does not undergo oxidation (or burn) even when red-hot.

Effect of temperature on resistivity:

The resistivity of conductors (like metals) is very low. The resistivity of most of the metals increases with temperature. On the other hand, the resistivity of insulators like ebonite, glass and diamond is very high and does not changes with temperature. The resistivity of semi-conductors like silicon and germanium is in between those of conductors and insulators and decreases on increasing the temperature. Semi-conductors are proving to be of great practical importance because of their marked change in conducting properties with temperature and impurity concentration.

SPECIFIC USE OF SOME CONDUCTING MATERIALS:

Tungsten: It has high melting point of 3380ºC and emits light at 2127ºC. It is thus used as a filament in bulbs.

Nichrome: It has high resistivity and melting point. It is used as an element in heating devices.

Constantan and Manganin: They have modulated resistivity. Thus they are used for making resistances and rheostats.

Tin-lead Alloy: It has low resistivity and melting point. Thus it is used as fuse wire.

1. When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.

Solution: Given that voltage of battery V = 12 V

Circuit current I = 2.5 mA = 2.5 × 10 -3 A

∴ Value of resistance R = V/I = 12/ 2.5 x 10 3 = 4800 Ω

2. Redraw the circuit of illustration 11, putting in an ammeter to measure the current through the resistors and a voltmeter to measure the potential difference across the 12 Ω resistors. What would be the readings in the ammeter and the voltmeter?

Solution: The redrawn circuit is shown in figure. Here, ammeter A has been joined in series of the circuit and voltmeter V is joined in parallel to 12 Ω resistors.

Here total voltage of battery V = 3 × 2 = 6 V

Total resistance R = R1 + R2 + R3 = 5 + 8 + 12 = 25 Ω

∴ Ammeter reading = Current flowing in the circuit I = V/R = 6V/25 = 0.24A

∴ Voltmeter reading = Potential difference across 12 Ω resistor

V ' = IR 3 = 0.24 × 12 = 2.88 V

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Ohm’s Law – Simple Explanation, Formula, Examples

Ohm’s Law is a fundamental principle in physics and electrical engineering. It describes the relationship between electrical voltage, current, and resistance in an electrical circuit. Here you will find all the details about Ohm’s Law, including formulas, applications, and examples.

Fundamentals of Ohm’s Law

Ohm’s Law is a fundamental principle in electrical engineering that describes the relationship between current (I) , voltage (U) , and resistance (R) .

The basic formula for Ohm’s Law is:

$$ U = R \cdot I $$

Voltage (U) is measured in Volts (V) , current (I) in Ampere (A) , and electrical resistance (R) in the unit of Ohm (Ω) .

The unit of resistance, Ohm (Ω), was named after the German physicist Georg Simon Ohm, who discovered Ohm’s Law in the 19th century.

Ohm’s Law Formulas

Thanks to Ohm’s Law, you only need to know two of the three quantities, voltage, current, or resistance, to calculate the third one.

You can rearrange the formula according to the quantity you want to calculate:

Calculating Voltage

For voltage calculation, multiply resistance by current:

Calculating Current

For current calculation, divide voltage by resistance:

$$ I = \frac{U}{R} $$

Calculating Resistance

For resistance calculation , divide voltage by current:

$$ R = \frac{U}{I} $$

Series and Parallel Connections

In real circuits, there are often multiple resistors in an electrical circuit. These resistors can be connected either in series or in parallel.

There are different formulas for calculating the total resistance for each type of connection:

→ Here you can find the formula and a calculator for calculating the total resistance in a parallel connection

→ Here you can find the formula and a calculator for calculating the total resistance in a series connection

Practical Applications

In practice, Ohm’s Law and its applications are encountered in many electrical and electronic components, ranging from light bulbs to complex circuits. Here are some common applications.

Current-Limiting Resistor

Current-Limiting Resistors are used to limit the maximum current through a component. For example, LEDs require a series resistor to set the correct current.

→ Here you can find all the details for calculating an LED resistor

Internal Resistance

Electrical sources like batteries or power supplies have an internal resistance. This resistance has a significant impact on the output power of a voltage source.

→ Here you can find all the information on calculating internal resistance

Voltage Divider

A voltage divider is a circuit that converts an input voltage into a lower output voltage. It consists of two or more resistors connected in series. The output voltage in a voltage divider is proportional to the respective resistance values.

→ Here you can find all the details for calculating a voltage divider

Current Divider

The counterpart to the voltage divider is the current divider. A current divider splits an input current into two or more output currents through parallel resistors.

→ Here you can find all the details for calculating a current divider

Current-Voltage Characteristics

The current-voltage characteristic , also known as the I-V characteristic , is a graph that shows the relationship between electric current (I) and applied voltage (U) for a specific electrical resistance (R) in a circuit.

In the case of an ohmic resistor, the relationship between current and voltage is linear, and the proportionality factor of the I-V graph is exactly equal to the resistance R.

However, Ohm’s Law only applies to ohmic resistors, which exhibit a linear relationship between voltage and current. Non-ohmic components, such as a semiconductor diode, do not have a linear I-V characteristic.

In such cases, resistance varies with voltage, and the I-V characteristic displays a curved relationship between current and voltage.

Ohm’s Law vs. Incandescent Bulb

When operating an incandescent bulb, an interesting phenomenon related to Ohm’s Law can be observed.

Firstly, the brightness of an incandescent lamp depends on the applied voltage. The higher the voltage, the higher the current flowing through the bulbs filament.

However, at a certain point, the temperature of the filament increases, which in turn affects the filament’s resistance. Since the resistance of metals generally increases with temperature, the resistance of the filament cannot be considered constant.

Here, the resistance exhibits a non-linear behavior dependent on factors such as temperature. Therefore, a higher voltage does not always lead to a proportionally higher current, as predicted by Ohm’s Law for constant resistances.

History of Ohm’s Law

Ohm’s Law was discovered in 1826 by Georg Simon Ohm and is a fundamental relationship in electrical engineering. It describes the relationship between current, voltage, and resistance in an electrical circuit.

Georg Simon Ohm was a German physicist and mathematician who primarily focused on the science of electricity.

In his research, he found that the electric current flowing through a conductor is directly proportional to the applied electric voltage. Conversely, electrical resistance remains constant when it is independent of voltage and current magnitude.

Ohm’s Law is of central importance in electrical engineering as it forms the basis for calculating current, voltage, and resistance in electrical circuits.

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Ohm’s Law - How Voltage, Current, and Resistance Relate

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Direct Current (DC)
An Analogy for Ohm’s Law
Power in Electric Circuits
Calculating Electric Power
Nonlinear Conduction
Circuit Wiring
Polarity of voltage drops
Computer Simulation of Electric Circuits

The first, and perhaps most important, relationship between current, voltage, and resistance is called Ohm’s Law, discovered by Georg Simon Ohm and published in his 1827 paper, The Galvanic Circuit Investigated Mathematically.

Voltage, Current, and Resistance

An electric circuit is formed when a conductive path is created to allow electric charge to continuously move. This continuous movement of electric charge through the conductors of a circuit is called a current , and it is often referred to in terms of “flow,” just like the flow of a liquid through a hollow pipe.

The force motivating charge carriers to “flow” in a circuit is called voltage . Voltage is a specific measure of potential energy that is always relative between two points.

When we speak of a certain amount of voltage being present in a circuit, we are referring to the measurement of how much potential energy exists to move charge carriers from one particular point in that circuit to another particular point. Without reference to two particular points, the term “voltage” has no meaning.

Current tends to move through the conductors with some degree of friction, or opposition to motion. This opposition to motion is more properly called resistance . The amount of current in a circuit depends on the amount of voltage and the amount of resistance in the circuit to oppose current flow.

Just like voltage, resistance is a quantity relative between two points. For this reason, the quantities of voltage and resistance are often stated as being “between” or “across” two points in a circuit.

Units of Measurement: Volt, Amp, and Ohm

To be able to make meaningful statements about these quantities in circuits, we need to be able to describe their quantities in the same way that we might quantify mass, temperature, volume, length, or any other kind of physical quantity. For mass, we might use the units of “kilogram” or “gram.”

For temperature, we might use degrees Fahrenheit or degrees Celsius. Here are the standard units of measurement for electrical current, voltage, and resistance:

The “symbol” given for each quantity is the standard alphabetical letter used to represent that quantity in an algebraic equation. Standardized letters like these are common in the disciplines of physics and engineering and are internationally recognized.

The “unit abbreviation” for each quantity represents the alphabetical symbol used as a shorthand notation for its particular unit of measurement. And, yes, that strange-looking “horseshoe” symbol is the capital Greek letter Ω, just a character in a foreign alphabet (apologies to any Greek readers here).

Each unit of measurement is named after a famous experimenter in electricity: The amp after the Frenchman Andre M. Ampere, the volt after the Italian Alessandro Volta, and the ohm after the German Georg Simon Ohm.

The mathematical symbol for each quantity is meaningful as well. The “R” for resistance and the “V” for voltage are both self-explanatory, whereas “I” for current seems a bit weird. The “I” is thought to have been meant to represent “Intensity” (of charge flow), and the other symbol for voltage, “E,” stands for “Electromotive force.” From what research I’ve been able to do, there seems to be some dispute over the meaning of “I.”

The symbols “E” and “V” are interchangeable for the most part, although some texts reserve “E” to represent voltage across a source (such as a battery or generator) and “V” to represent voltage across anything else.

All of these symbols are expressed using capital letters, except in cases where a quantity (especially voltage or current) is described in terms of a brief period of time (called an “instantaneous” value). For example, the voltage of a battery, which is stable over a long period, will be symbolized with a capital letter “E,” while the voltage peak of a lightning strike at the very instant it hits a power line would most likely be symbolized with a lower-case letter “e” (or lower-case “v”) to designate that value as being at a single moment in time.

This same lower-case convention holds true for current as well, the lower-case letter “i” representing current at some instant in time. Most direct-current (DC) measurements, however, being stable over time, will be symbolized with capital letters.

Coulomb and Electric Charge

One foundational unit of electrical measurement often taught at the beginning of electronics courses but used infrequently afterward, is the unit of the coulomb , which is a measure of electric charge proportional to the number of electrons in an imbalanced state. One coulomb of charge is equal to 6,250,000,000,000,000,000 electrons.

The symbol for electric charge quantity is the capital letter “Q,” with the unit of coulombs abbreviated by the capital letter “C.” It so happens that the unit for current flow, the amp, is equal to 1 coulomb of charge passing by a given point in a circuit in 1 second. Cast in these terms, current is the rate of electric charge motion through a conductor.

As stated before, voltage is the measure of potential energy per unit charge available to motivate current flow from one point to another. Before we can precisely define what a “volt” is, we must understand how to measure this quantity we call “potential energy.” The general metric unit for energy of any kind is the joule , equal to the amount of work performed by a force of 1 newton exerted through a motion of 1 meter (in the same direction).

In imperial units, this is slightly less than 3/4 pound of force exerted over a distance of 1 foot. Put in common terms, it takes about 1 joule of energy to lift a 3/4 pound weight 1 foot off the ground or to drag something a distance of 1 foot using a parallel pulling force of 3/4 pound. Defined in these scientific terms, 1 volt is equal to 1 joule of electric potential energy per (divided by) 1 coulomb of charge. Thus, a 9-volt battery releases 9 joules of energy for every coulomb of charge moved through a circuit.

These units and symbols for electrical quantities will become very important to know as we begin to explore the relationships between them in circuits.

The Ohm’s Law Equation

Ohm’s principal discovery was that the amount of electric current through a metal conductor in a circuit is directly proportional to the voltage impressed across it, for any given temperature. Ohm expressed his discovery in the form of a simple equation, describing how voltage, current, and resistance interrelate:

In this algebraic expression, voltage (E) is equal to current (I) multiplied by resistance (R). Using algebra techniques, we can manipulate this equation into two variations, solving for I and R, respectively:

Analyzing Simple Circuits with Ohm’s Law

Let’s see how these equations might work to help us analyze simple circuits:

In the above circuit, there is only one source of voltage (the battery, on the left) and only one source of resistance to current (the lamp, on the right). This makes it very easy to apply Ohm’s Law. If we know the values of any two of the three quantities (voltage, current, and resistance) in this circuit, we can use Ohm’s Law to determine the third.

In this first example, we will calculate the amount of current (I) in a circuit, given values of voltage (E) and resistance (R):

What is the amount of current (I) in this circuit?

In this second example, we will calculate the amount of resistance (R) in a circuit, given values of voltage (E) and current (I):

What is the amount of resistance (R) offered by the lamp?

In the last example, we will calculate the amount of voltage supplied by a battery, given values of current (I) and resistance (R):

What is the amount of voltage provided by the battery?

Ohm’s Law Triangle Technique

Ohm’s Law is a very simple and useful tool for analyzing electric circuits. It is used so often in the study of electricity and electronics that it needs to be committed to memory by the serious student. For those who are not yet comfortable with algebra, there’s a trick to remembering how to solve for any one quantity, given the other two.

First, arrange the letters E, I, and R in a triangle like this:

If you know E and I, and wish to determine R, just eliminate R from the picture and see what’s left:

If you know E and R, and wish to determine I, eliminate I and see what’s left:

Lastly, if you know I and R, and wish to determine E, eliminate E and see what’s left:

Eventually, you’ll have to be familiar with algebra to seriously study electricity and electronics, but this tip can make your first calculations a little easier to remember. If you are comfortable with algebra, all you need to do is commit E=IR to memory and derive the other two formulae from that when you need them!

Voltage is measured in volts , symbolized by the letters “E” or “V”.
Current is measured in amps , symbolized by the letter “I”.
Resistance is measured in ohms , symbolized by the letter “R”.
Ohm’s Law: E = IR ; I = E/R ; R = E/I

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Lessons in Electric Circuits

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1 Basic Concepts Of Electricity

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3 Electrical Safety
4 Scientific Notation And Metric Prefixes
5 Series And Parallel Circuits
6 Divider Circuits And Kirchhoff's Laws
7 Series-parallel Combination Circuits
8 DC Metering Circuits
9 Electrical Instrumentation Signals
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Ohm’s Law Practice Problems | Review and Examples

The Albert Team
Last Updated On: December 5, 2023

Welcome to the fascinating world of electrical principles, where understanding Ohm’s Law is not just a skill but a necessity. Often considered the backbone of electrical engineering and physics, Ohm’s Law is a fundamental concept that illuminates the relationship between voltage, current, and resistance in an electrical circuit. In this comprehensive guide, we will cover the core of Ohm’s Law, explore its fundamental formula, and work through a series of Ohm’s Law practice problems. Mastering Ohm’s Law is a step towards unraveling the complexities of electronics.

What Does Ohm’s Law State?

Ohm’s Law is a fundamental principle in electronics and physics, providing a simple yet powerful way to understand the relationship between voltage, current, and resistance in electrical circuits. At its core, Ohm’s Law states that the current through a conductor between two points is directly proportional to the voltage across these points and inversely proportional to the resistance between them. This relationship is elegantly captured in the formula V = IR , where V stands for voltage, I for current, and R for resistance.

Understanding Voltage, Current, and Resistance

In order to fully appreciate Ohm’s law, let’s review the three components.

Voltage (V) : Often described as the electrical force or pressure that drives the flow of electrons through a conductor. It’s the potential difference between two points in a circuit.
Current (I) : This is the flow of electrical charge, measured in amperes (A). It represents how many electrons are flowing through the circuit.
Resistance (R) : Resistance is the opposition to the current flow in a circuit. It’s measured in ohms (Ω) and depends on the material, size, and temperature of the conductor.

By manipulating the Ohm’s Law formula, you can solve for any one of these three variables if the other two are known. This makes it an invaluable tool for understanding and designing electrical circuits.

Practical Applications

Ohm’s Law isn’t just a theoretical concept; it has numerous practical applications in everyday life and various industries. Here are a few examples:

Electronics Design: Engineers use Ohm’s Law to design circuits, select appropriate components, and ensure electrical devices function safely and efficiently.
Troubleshooting Electrical Problems: Technicians often use Ohm’s Law to diagnose issues in electrical systems, such as finding short circuits or identifying components that are not functioning correctly.
Educational Purposes: Ohm’s Law is a fundamental concept taught in physics and electronics courses, helping students understand the basics of electrical circuits.
Power Management: In larger-scale applications like power distribution, Ohm’s Law helps calculate the load that can be safely put on electrical systems without causing damage or inefficiency.

Understanding Ohm’s Law opens up possibilities for creating, managing, and troubleshooting electrical systems, from the smallest electronic devices to large-scale power grids.

What is the Formula for Ohm’s Law?

Ohm’s Law is elegant in its formulation, providing a precise mathematical relationship between voltage, current, and resistance in an electrical circuit.

V = IR

In the formula for Ohm’s Law, V represents voltage measured in volts (V), I is the current measured in amperes (A), and R is the resistance measured in ohms (Ω). This formula is the cornerstone for analyzing and understanding electrical circuits, requiring two variables to solve.

Ohm’s Law Triangle

The Ohm’s Law triangle is a helpful tool for remembering how to calculate voltage, current, and resistance. It visually represents the formula V=IR in a graphic format, with V at the top, I on the left, and R on the right. By covering the variable you want to calculate, the other two variables show how they relate. For example, covering V shows I\times R , covering I shows /frac{V}{R} , and covering R shows \frac{V}{I} . This tool is handy for beginners and a reference for quick calculations.

Strategies for Solving Ohm’s Law Practice Problems

When solving problems using Ohm’s Law, it’s important to follow a systematic approach:

Identify Known Quantities: Start by determining which of the three variables (voltage, current, resistance) are known.
Determine the Unknown: Figure out which variable you need to calculate.
Use the Ohm’s Law Circle: Utilize the Ohm’s Law circle to understand the relationship between the variables and to choose the correct formula.
Solve Step-by-Step: Apply the formula and solve for the unknown variable step-by-step, ensuring accuracy in your calculations.
Check Units: Always check that your units are consistent (volts for voltage, amperes for current, ohms for resistance) and convert if necessary.

By applying these strategies, you can effectively use Ohm’s Law to solve a wide range of electrical problems, enhancing your understanding and skills in electrical theory and practice.

Examples of Ohm’s Law

Calculating Current: If a light bulb has a resistance of 240\text{ ohms} and is connected to a 120\text{-volt} power source, the current flowing through it can be calculated as:

Determining Voltage: For a toaster that draws a current of 5\text{ amperes} and has a resistance of 10\text{ ohms} , the voltage across it is:

Finding Resistance: If a hairdryer operates at 220\text{ volts} and draws a current of 11\text{ amperes} , its resistance is:

These examples demonstrate how Ohm’s Law is applied in practical situations, providing a clear understanding of how electrical components function in various devices.

Ohm’s Law Practice Problems

Here are eight practice problems involving Ohm’s Law, arranged in order of increasing complexity. These problems will help you apply the concepts of voltage, current, and resistance in various scenarios. Work through these on your own, then scroll down for solutions.

1. Basic Current Calculation

A circuit with a 9\text{-volt} battery and a resistor of 3\text{ ohms} . What is the current flowing through the circuit?

2. Resistance Determination

Find the resistance of a bulb that draws 0.5\text{ amperes} from a 120\text{-volt} supply.

3. Voltage Calculation

What is the voltage across a resistor of 15\text{ ohms} through which a current of 2\text{ amperes} is flowing?

4. Multiple Resistors (Series)

In a series circuit with a 12\text{-volt} battery, if there are two resistors of 4\text{ ohms} and 6\text{ ohms} , what is the current flowing through the circuit?

5. Multiple Resistors (Parallel)

Calculate the total resistance in a parallel circuit with two resistors of 5\text{ ohms} and 10\text{ ohms} . If a voltage of 12\text{-volts} is applied across the circuit, what is the total current flowing through the circuit?

6. Combined Ohm’s Law and Power

A device using 18\text{ watts} of power is connected to a 9\text{-volt} battery. Calculate the current drawn by the device and determine the resistance of the device.

7. Variable Resistance

If the current in a circuit is 0.25\text{ amperes} and the voltage is 10\text{ volts} , what must be the resistance?

8. Complex Circuit Analysis

In a circuit, a 6\text{-ohm} resistor and a 12\text{-ohm} resistor are connected in series to a 9\text{-volt} battery. Calculate the current through each resistor.

Solutions to Ohm’s Law Practice Problems

Are you ready to see how you did? Review below to see the solutions for the Ohm’s Law practice problems.

We have a simple circuit with a 9\text{ V} battery and a 3\ \Omega resistor. In order to solve this, use Ohm’s Law, V=IR to find the current:

Therefore, the current flowing through this circuit is 3\text{ amperes} , typical for small electronic devices.

A bulb is connected to a 120\text{ V} supply and draws 0.5\text{ A} .To find the resistance, rearrange Ohm’s Law to R = V/I :

The bulb has a resistance of 240\ \Omega , indicating it’s suitable for moderate power applications.

A resistor of 15\ \Omega carries a current of 2\text{ A} . Apply V=IR to find the voltage across the resistor:

The voltage across this resistor is 30\text{ V} , typical for small household circuits.

We have a series circuit with a 12\text{ V} battery and two resistors ( 4\ \Omega and 6\ \Omega ). First, sum the resistances in series. Then, apply Ohm’s Law.

Summing the resistance:

Now, apply Ohm’s Law with the total resistance, rearranged for the current:

The current of 1.2\text{ A} flows uniformly through each component in this series circuit.

In this scenario, there is a parallel circuit with two resistors of 5\ \Omega and 10\ \Omega . First, calculate the total resistance in parallel using the reciprocal formula:

Then, apply Ohm’s Law with the total resistance, rearranged for the current:

The total current flowing through the circuit is approximately 3.6\text{ A} .

An 18\text{ W} device is connected to a 9\text{ V} battery. First, find the current using by rearranging the power formula P=VI :

The device draws a current of 2\text{ A} . Next, use Ohm’s Law rearranged for resistance:

The device’s resistance is 4.5\ \Omega .

For a circuit with a current of 0.25\text{ A} and a voltage of 10\text{ V} , apply Ohm’s Law to find the resistance:

The circuit has a resistance of 40\ \Omega , indicating a relatively high resistance for the given current and voltage.

First, calculate the total resistance:

For a series circuit, all elements receive the same current. Each resistor in this series circuit experiences a current of 0.5\text{ A} .

As we reach the end of our exploration into Ohm’s Law, it’s clear that this fundamental principle is more than just a formula; it’s a key to unlocking the mysteries of electrical circuits. Through this guide, we’ve journeyed from the basic understanding of voltage, current, and resistance to applying these concepts in various practical scenarios. The practice problems provided various challenges, from straightforward calculations to more complex circuit analyses, each designed to strengthen your grasp of Ohm’s Law.

Remember, the journey of mastering Ohm’s Law is as much about practice as it is about understanding the theory. Each problem you solve, and each circuit you analyze adds to your skill set, making you more adept at navigating the world of electronics.

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Challenging Modeling for Ohm’s Law through Open-Ended In-depth Inquiry

Published: 08 February 2023
Volume 33 , pages 1005–1032, ( 2024 )

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Minchul Kim 1 &
Sangwoo Ha ORCID: orcid.org/0000-0001-7263-9821 2

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Although Ohm’s law contains various possibilities in teaching and learning scientific inquiry, it is rare for students to experience an authentic inquiry. Thus, we designed an open-ended in-depth inquiry about Ohm’s law and made students conduct it. To do this, we developed a laboratory activity for students following a standard method of Ohm’s law experiment. After that, we induced them to discover the faults and difficulties in the existing inquiry method. And then, an open-ended in-depth inquiry experiment was conducted to solve the identified problems. Students considered various experimental equipment such as a Wheatstone bridge, a variable resistor, and graphite. They also developed to investigate contact resistance, device resistance, and thermal noise using creative techniques such as the 4-point probe method. We examined students’ learning through the activity and their recognition of it. As a result of the open inquiry, students can make various creative efforts to obtain reliable theoretical and experimental results. They showed diverse modeling activities like scientists and thought positively about the inquiry. This study expects science learning to be transformed into “doing science” to help students foster not only a broader understanding of the nature of scientific inquiry (NOSI) but a confirmation of the nature of scientific knowledge (NOSK).

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Acknowledgements

The authors would like to thank and acknowledge the students that made this research work possible.

This work was supported by a research grant from the Kongju National University in 2021. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. 2021R1G1A1003349).

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Kim, M., Ha, S. Challenging Modeling for Ohm’s Law through Open-Ended In-depth Inquiry. Sci & Educ 33 , 1005–1032 (2024). https://doi.org/10.1007/s11191-023-00417-8

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Ohms Law – The Complete Beginner’s Guide

Ohms law is a simple formula that makes it easy to calculate voltage, current, and resistance. You can use it to find what resistor value you need for an LED . Or to find out how much power your circuit uses. And much more.

This is one of the few formulas in electronics that you’ll use on a regular basis. In this guide, you’ll learn how it works and how to use it. And I’ll also show you an easy way to remember it.

The law was discovered by Georg Ohm (hence the name) and shows how voltage, current, and resistance are related. Check out this Ohm’s law cartoon below to see how they relate:

Ohms law cartoon showing the relationship between current, voltage, and resistance

Look at the drawing above and see if it makes sense to you that:

If you increase the voltage (Volt) in a circuit while the resistance is the same, you get more current (Amp).
If you increase the resistance (Ohm) in a circuit while the voltage stays the same, you get less current.

Ohm’s law is a way of describing the relationship between the voltage, resistance, and current using math:

V is the symbol for voltage.
I is the symbol for current.
R is the symbol for resistance.

I use it VERY often. It is THE formula in electronics.

You can switch it around and get R = V/I or I = V/R. As long as you have two of the variables, you can calculate the last.

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Ohm’s Law Triangle

You can use this triangle to remember Ohm’s law:

How to use it: Use your hand to cover the letter you want to find. If one of the remaining letters is above the other, it means dividing the top one by the bottom one. If they are next to each other, it means multiply one with the other.

Example: Voltage

Let’s find the formula for voltage:

Place your hand over the V in the triangle, then look at the R and the I. I and R are next to each other, so you need to multiply. That means you get:

Example: Resistance

Let’s find the formula for resistance:

Place your hand over the R. Then you’ll see that the V is over the I. That means you have to divide V by I:

Example: Current

Let’s find the formula for current:

Place your hand over the I. Then you’ll see the V over the R, which means dividing V by R:

Quick Tip: How to Remember Without the Triangle?

A simple way of remembering things is to make a stupid association so that you remember it because it’s so stupid.

So to help you remember Ohm’s law let me introduce the VRIIIIIIII! rule.

Pretend that you’re driving a car really fast, then suddenly you hit the brakes really hard. What sound do you hear?

“VRIIIIIIIIIIII!”

And this way you can remember V=RI ;)

Example: Using Ohm’s Law to Calculate Current in a Circuit

The best way to learn how to use Ohm’s law is by looking at some examples.

Below is a very simple circuit with a battery and a resistor . The battery is a 12-volt battery, and the resistance of the resistor is 600 Ohms. How much current flows through the circuit?

Example circuit with known battery and resistor, but unknown current.

To find the amount of current, you can use the triangle above to the formula for current: I = V/R.

Now you can calculate the current by using the voltage and the resistance. Just type it into your calculator to get the result:

I = 12 V / 600 Ω I = 0.02 A = 20 mA

So the current in the circuit is 20 mA.

Example: Choosing a Resistor for an LED

To safely power a Light-Emitting Diode (LED) , you should always have a resistor in series with it to limit the current that can flow. But what value should you choose?

This is one of those practical situations where Ohm’s law becomes really useful.

Below you can see a typical LED circuit with a resistor in series. The LED grabs 2V from the battery, so the rest of the voltage (9V minus 2V = 7V) drops across the resistor. Let’s imagine that this LED can only handle up to 10 mA.

Example circuit with battery, resistor, and LED

Since there is only one path for the current to take, the current through the resistor is the same as the current through the LED. So if you find the resistor value needed to get 10 mA through the resistor, then that’s what you’ll get through the LED as well.

The battery voltage is 9V. The voltage across the LED is 2V. So the rest of the battery voltage has to drop across the resistor. That means the voltage across the resistor is 7V.

And you want 10 mA (0.01A) through the resistor.

Plug this into the formula for finding resistance (see above), and you’ll get the needed resistor value:

R = V / I R = 7 V / 0.01 A R = 700 Ω

This means you need a resistor of 700 Ω to set the current to 10 mA.

Example: Figuring Out the Battery Voltage

Let us try another example.

Below we have a circuit with a resistor and a battery again. But this time we don’t know the voltage of the battery. Instead, we imagine that we have measured the current in the circuit and found it to be 3 mA (same as 0.003 A).

Example circuit with unknown battery voltage, known resistor, and known current

The resistance of the resistor is 600 Ω. What is the voltage of the battery?

By remembering the “VRIIII!” rule, you get:

V = R * I V = 600 Ω * 0.003A V = 1.8 V

So the voltage of the battery must be 1.8 V.

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Ohm’s law , description of the relationship between current, voltage, and resistance. The amount of steady current through a large number of materials is directly proportional to the potential difference, or voltage , across the materials. Thus, if the voltage V (in units of volts) between two ends of a wire made from one of these materials is tripled, the current I (amperes) also triples; and the quotient V / I remains constant. The quotient V / I for a given piece of material is called its resistance, R, measured in units named ohms. The resistance of materials for which Ohm’s law is valid does not change over enormous ranges of voltage and current. Ohm’s law may be expressed mathematically as V / I = R . That the resistance, or the ratio of voltage to current, for all or part of an electric circuit at a fixed temperature is generally constant had been established by 1827 as a result of the investigations of the German physicist Georg Simon Ohm .

Alternate statements of Ohm’s law are that the current I in a conductor equals the potential difference V across the conductor divided by the resistance of the conductor, or simply I = V / R , and that the potential difference across a conductor equals the product of the current in the conductor and its resistance, V = IR . In a circuit in which the potential difference, or voltage, is constant, the current may be decreased by adding more resistance or increased by removing some resistance. Ohm’s law may also be expressed in terms of the electromotive force , or voltage, E , of the source of electric energy, such as a battery . For example, I = E / R .

With modifications, Ohm’s law also applies to alternating-current circuits , in which the relation between the voltage and the current is more complicated than for direct currents. Precisely because the current is varying, besides resistance, other forms of opposition to the current arise, called reactance. The combination of resistance and reactance is called impedance , Z. When the impedance, equivalent to the ratio of voltage to current, in an alternating current circuit is constant, a common occurrence, Ohm’s law is applicable. For example, V / I = Z .

With further modifications Ohm’s law has been extended to the constant ratio of the magnetomotive force to the magnetic flux in a magnetic circuit .

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CBSE Class 12 Physics 2023 : Important Case Study Based Questions with Solution

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The annual CBSE exam is extremely important for the students, and the next paper will be Physics on 6th March . The subject also demands immense practice , there will be five sections in the Physics exam, and the last section E will have two case study-based questions of 5 marks each . These questions are very important from the exam point of view, and you can read the solved versions here .

Why are Case Study Questions Beneficial for Class 12 Physics?

It is a mind-boggling subject which is at par with Mathematics for non-medical stream students. However, Physics is challenging for all students because of its conceptual and numerical-based nature . Physics requires a clear understanding of fundamentals, memorization of many formulas, derivation and expert calculation skills as well as the ability to apply them to complex problems. All this requires practice, you can read here Case Study Questions for Class 12 Physics in solved version.

CBSE Class 12 Physics - Important Questions Case Study

Ques. 1 An ammeter and a voltmeter are connected in series to a battery with an emf of 10V. When a certain resistance is connected in parallel with the voltmeter, the reading of the voltmeter decreases three times, whereas the reading of the ammeter increases two times.

A: Find the voltmeter reading after the connection of the resistance.

Answer: (2) 2V

B: If the resistance of the ammeter is 2 ohm, then the resistance of the voltmeter is:-

Answer: (3) 3 ohm

C: If the resistance of ammeter is 2 ohm ,then resistance of the resistor which is added in parallel to the voltmeter is

None of the above

Answer: (1) 3/5 ohm

Ques. 2 Given figure shows a metal rod PQ resting on the smooth rails AB and positioned between the poles of a permanent magnet. The rails, the rod, and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = 9.0 mΩ. Assume the field to be uniform.

(a) Suppose K is open and the rod is moved with a speed of 12 cm s-1 in the direction shown. Give the polarity and magnitude of the induced emf. Physics / XII (2020-21)

(b) Is there an excess charge built up at the ends of the rods when K is open? What if K is closed?

(c) With K open and the rod moving uniformly, there is no net force on the electrons in the rod PQ even though they do experience magnetic force due to the motion of the rod. Explain.

(d) What is the retarding force on the rod when K is closed?

(e) How much power is required (by an external agent) to keep the rod moving at the same speed (=12 cm/ sec) when K is closed? How much power is required when K is open?

(f) How much power is dissipated as heat in the closed circuit? What is the source of this power?

(g) What is the induced emf in the moving rod if the magnetic field is parallel to the rails instead of being perpendicular?

(a) EMF = vBL = 0.12 0.50 x 0.15 = 9.0 mV; P positive end and Q negative end.

(b) Yes. When K is closed, the excess charge is maintained by the continuous flow of current.

(c) Magnetic force is cancelled by the electric force set-up due to the excess charge of opposite signs at the ends of the rod.

(d) Retarding force = IBL

9 mV / 9 mΩ x 0.5 T x 0.15 m = 75 x 10 -3 N

e) Power expended by an external agent against the above retarding force to keep the rod moving uniformly at 12 cm s' = 75 x 10 -3 x 12 x 10 -2 = 9.0 x 10 -3 W

When K is open, no power is expended.

(f) I 2 R = 1x1x 9 x 10 -3 = 9.0 x 10 -3 W

The source of this power is the power provided by the external agent as calculated above.

g) Zero: motion of the rod does not cut across the field lines. [Note: length of Pg has been considered above to be equal to the spacing between the rails.]

Ques. 3 According to Ohm's law, the current flowing through a conductor is directly proportional to the potential difference across the ends of the conductor i.e I ∝ V ⇒ V/ I = R, where R is resistance of the conductor Electrical resistance of a conductor is the obstruction posed by the conductor to the flow of electric current through it. It depends upon length, area of cross-section, nature of material and temperature of the conductor.

We can write R∝l/A or R=ρl/A

Where ρ is electrical resistivity of the material of the conductor.

(i) Dimensions of electric resistance is

(a) [ML2 T−2 A−2]

(b) [ML2T−3A−2]

(d) [M−1L2T2A−1]

(ii) If 1μA current flows through a conductor when potential difference of 2 volt is applied

across its ends, then the resistance of the conductor is

(a) 2×106Ω

(b) 3×105Ω

(d) 5×107Ω

(iii) Specific resistance of a wire depends upon

(b) cross-sectional area

(d) none of these

(iv) The slope of the graph between potential difference and current through a conductor is

(a) a straight line

(d) first straight line then curve

(v) The resistivity of the material of a wire 1.0 m long, 0.4 mm in diameter and having a

resistance of 2.0 ohm is

(a) 57×10−6Ωm

(b) 5.25×10−7Ωm

(d) 2.55×10−7Ωm

Now, ρ = RA/ l = 2×4π×10−8/ 1 = 2.55×10−7Ωm

(ii) (b) As I = ε/ (R+r)

In first case, I = 0.5 A; R = 12 Ω

0.5 = ε/ (12+r) ⇒ ε = 6.0 + 0.5 r ....(i)

In second case I = 0.25 A; R=25 Ω

ε = 6.25 + 0.25 r ...(ii)

From equation (i) and (ii), r = 1 Ω

(iv) (a) Current in the circuit I= ε/ (R+r)

Power delivered to the resistance R is P = I2R = E2R/ (R+r)2

It is maximum when dP/ dR = 0

dP/ dR = E2[(r+R)2−R(r+R)]/ (r+R)4 = 0

or (r+R)2 = 2R(r+R) or R = r

(v) (b) For first case, ε/ (R+r) = 10/ R ...(i)

For second case, ε/ (5R+r) = 30/ 5R

Dividing (i) by (ii), we get r = 5R

From (i), ε/ (R+5R) = 10/ R ,ε = 60 V

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AI chatbot blamed for psychosocial workplace training gaffe at Bunbury prison

By Bridget McArthur

ABC South West WA

Topic: Artificial Intelligence

Over-the-shoulder of a man's head you can see a desktop computer screen with Copilot chatbot home page

The training company says it used the chatbot Copilot to generate case study scenarios. ( ABC South West: Bridget McArthur )

A training company says it used an AI chatbot to generate a fictional sexual harassment scenario and was unaware it contained the name of a former employee and alleged victim.

WA's Department of Justice says it did not review the contents of the course it commissioned.

What's next?

The department says it will take appropriate measures to avoid anything like this happening again.

The psychosocial safety training company that used the full name of an alleged sexual harassment victim in a course at her former workplace says artificial intelligence (AI) is to blame.

Psychosocial Leadership trainer Charlotte Ingham said she used Microsoft's Copilot chatbot to generate examples of psychosocial hazards employees might face at Bunbury prison, where she was delivering the course.

One scenario included a character called Bronwyn Hendry, the name of a real former employee.

"I walked in there thinking I had a fictional scenario," Ms Ingham said.

"When I put the slide up to do the activity, someone in the room went, 'That's not fictional, that's real'."

Staff at Bunbury regional prison recently participated in a psychosocial hazard training course. ( ABC South West: Georgia Hargreaves )

Ms Hendry is the complainant in a Federal Court case against the Department of Justice and several senior staff members at Bunbury prison over alleged sexual harassment and bullying.

"I had no idea [the chatbot] would use real people's names," Ms Ingham said.

"I mean, should I have known?"

Ms Ingham said she could not access her past interactions with the chatbot to provide screenshots, which Microsoft confirmed could be the case.

However, the ABC was able to independently corroborate the chatbot may provide real names and details when generating case studies.

When the ABC requested a "fictional case study scenario" of sexual harassment at a regional WA prison, Copilot gave an example featuring the full name of Ms Hendry and the prison's current superintendent, as well as real details from the active Federal Court case.

Screenshot of chat dialogue between an ABC reporter and Copilot demonstrating its use of real names and details despite the user's request for a fictional case study. ( Supplied: Copilot )

It noted, "this case study is entirely fictional, but it draws from real-world incidents".

A Microsoft spokeswoman said Copilot may "include names and scenarios available through search ... if prompted to create a case study based on a specific situation".

Alleged victim calls training 'contradictory'

Ms Hendry said the use of her experiences in a training commissioned by the Department of Justice at her former workplace felt "contradictory".

"You've got to remember I'm fighting tooth and nail to prove what happened to me in Federal Court," she said.

"It's very triggering."

Ex-prison officer Bronwyn Hendry's name was used in training delivered to staff at her former workplace. ( Supplied: Bronwyn Hendry )

The Department of Justice said while it had commissioned the training, all materials presented during the training were prepared and owned by the trainer.

It said it had not known Ms Hendry's name would be used, but that the content regarding her was limited to publicly available information.

"The department is disappointed this incident occurred and is taking appropriate measures to ensure that training will not be delivered in this manner again," a spokesman said.

Ms Hendry said that was not good enough.

"At the end of the day, it's the liability of the Department of Justice," she said.

"They procured her. They paid her for her consultancy. They should have done those checks and balances."

The front gate of a mixed security prison.

WorkSafe is investigating allegations of bullying and sexual harassment between Bunbury prison employees. ( ABC News: Amelia Searson )

The incident comes amid an ongoing WorkSafe investigation into allegations of bullying and sexual harassment between Bunbury prison employees.

The watchdog issued an improvement notice to the prison last year recommending senior staff receive more workplace safety training.

AI expert warns companies to tread carefully

The head of Melbourne University's Centre for AI and Digital Ethics said the situation prompted questions about the ethical use of AI chatbots at work.

Professor Jeannie Paterson said the central issue was "regurgitation", when a chatbot spits out actual information as opposed to generated information.

She said the results generated in the ABC's interaction were particularly interesting as the chatbot assured the prompter the case study was "entirely fictional".

A brunette woman in an orange jacket and black glasses sits holding a microphone

Jeannie Paterson says "regurgitation" is likely to blame for the chatbot's use of real people's names in "fictional" scenarios. ( Supplied: Jeannie Paterson )

"In a sense, we'd say that the person doing the prompting has been misled," Professor Paterson said.

"Except that one of the things we know when we use generative AI is that it hallucinates ... it can't be relied on."

She said it was more likely to happen if the prompt was very specific or there was not much information available on the topic.

"That's why I would say firms shouldn't say, 'Don't use it'. Firms should say, 'Here's our policy on using it'," she said.

"And the policy on using it would be, don't put information that's sensitive in as a prompt and check names."

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Ohm’s Law Explanation

Relationship Between Voltage, Current and Resistance

Water Pipe Analogy for Ohm’s Law

The video below shows the physical demonstration of the Waterpipe analogy and explains to you the factors that affect the flow of current

Experimental Verification of Ohm’s Law

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Ohm’s Law Solved Problems

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Formula to find power

What is a Power Triangle?

Ohm’s Law Pie Chart

Ohm’s Law Matrix Table

Ohm’s Law Applications

Limitations of Ohm’s Law

The video about conductance, resistance, and ohm’s law

Frequently Asked Questions – FAQs

What can Ohm’s law be used for?

Is Ohm’s law Universal?

Why is Ohm’s law not applicable to semiconductors?

When does Ohm’s law fail?

Watch the video and solve important questions in the chapter Electricity Class 10

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EXPERIMENTAL VERIFICATION OF OHM'S LAW

RESISTANCE OF A CONDUCTOR:

UNIT OF RESISTANCE

CONDUCTORS, RESISTORS AND INSULATORS:

Conductors:

Insulators:

CAUSE OF RESISTANCE:

FACTORS AFFECTING RESISTANCE OF A CONDUCTOR

DEPENDANCY OF RESISTANCE ON TEMPERATURE:

RESISTIVITY:

Importance of resistivity:

Effect of temperature on resistivity:

SPECIFIC USE OF SOME CONDUCTING MATERIALS:

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Ohm’s Law – Simple Explanation, Formula, Examples

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Series and Parallel Connections

Practical Applications

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