Practice Faraday's Law in Physics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

The induced EMF in a circuit equals the negative rate of change of magnetic flux through the circuit.

The faster you change the magnetic field through a loop, the bigger the voltage you get. Faraday's law tells you exactly how much.

Showing a random 20 of 50 problems.

Example 1

easy
What law gives the direction of the induced current opposing the change in flux?

Example 2

challenge
A circular conducting loop of radius 0.05 m and resistance 0.02Ω lies perpendicular to a magnetic field that decreases at dB/dt=−3 T/s. Find the induced current and the power dissipated.

Example 3

hard
A 25-turn circular coil of radius 0.10 m lies in a field that changes uniformly from 0.30 T to 0.90 T in 0.5 s. Find the magnitude of the induced EMF.

Example 4

medium
A loop's flux is Φ(t)=3t (in Wb, t in s). Find the EMF in a single loop.

Example 5

easy
A 20-turn coil, flux changes by 0.5 Wb in 1 s. Find the EMF.

Example 6

easy
A 5-turn coil's flux per turn changes at 1.2 Wb/s. Find the magnitude of the induced EMF.

Example 7

medium
A 1.0 m2 single-loop coil sits in a vertical field. The field changes from +0.20 T (upward) to −0.20 T (downward) uniformly in 0.5 s. Find ∣E∣.

Example 8

easy
Faster flux change gives a bigger or smaller EMF?

Example 9

medium
A coil produces 12 V with flux changing at 0.6 Wb/s. Find the number of turns.

Example 10

easy
If the magnetic flux through a coil does not change, what is the induced EMF?

Example 11

hard
A square coil with 200 turns and side length 0.1 m is in a magnetic field that decreases uniformly from 0.5 T to 0 T in 0.2 s. Calculate the induced EMF. In which direction does the induced current flow (clockwise or anticlockwise, if the field points into the page)?

Example 12

medium
A 100-turn coil of area 0.02 m2 sits in a field rising at 3 T/s (perpendicular). Find the EMF.

Example 13

easy
What quantity does NΦ represent?

Example 14

easy
A 5-turn coil has flux changing at 4 Wb/s. Find the EMF.

Example 15

challenge
A square loop of side 0.3 m and 10 turns rotates at ω=20 rad/s in a 0.4 T field. Find the peak EMF.

Example 16

medium
A bar of length L=0.3 m slides at v=4 m/s perpendicular to a 0.5 T field through rails completing the circuit. Find the motional EMF.

Example 17

easy
What is the unit of magnetic flux ΦB?

Example 18

medium
A coil with N=80 has flux Φ=(0.005 Wb/s2) t2 per turn. Find the induced EMF magnitude at t=2 s.

Example 19

medium
A coil of 50 turns has an area of 0.01 m2. The magnetic field through it decreases from 0.8 T to 0.2 T in 0.5 s. What is the average induced EMF?

Example 20

challenge
A coil rotates so its flux is Φ(t)=0.5cos⁡(10t) Wb per turn, with N=20 turns. Find the peak EMF.
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