Unit 6: Electromagnetic Induction
Physics C: E&M · Unit 6 · Paper 3

Electromagnetic Induction unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1Paper 2Paper 3
Each paper is built from this unit’s 21 terms and is the same for everyone, so a teacher can assign “Unit 6, Paper 3” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.
Suggested time 37 min 34 points0/17 attempted
1

Why Lenz's law must hold

2

Motional EMF

3

Faraday's law

4

Maxwell's equations qualitatively

5

RL circuit

6

Lenz's law

7

Magnetic flux

8

Energy in an RL circuit

9

LC oscillation

10

Inductance

11

Force opposing motion

12

Mutual inductance

Short answer 1. Define or explain: Determining induced current direction

3 pts

Short answer 2. Define or explain: Energy stored in an inductor

3 pts

Short answer 3. Define or explain: Applying Lenz's law

3 pts

Short answer 4. Define or explain: Displacement current

3 pts

Free response

10 pts

Two long horizontal frictionless rails a distance L = 0.40 m apart lie in a uniform vertical magnetic field of magnitude B = 0.50 T. A conducting rod of mass m = 0.20 kg lies across the rails, and the circuit is completed by a resistor R = 2.0 Ω. The rod is given an initial speed v₀ = 6.0 m/s along the rails and then released.

Determine the initial emf and the initial current, and state the direction of the magnetic force on the rod.

Determine the initial magnitude of the rod’s acceleration.

Write the differential equation governing v(t) and show that v(t) = v₀e^(−t/τ) is its solution, identifying τ.

Evaluate τ and the speed at t = 5.0 s.

Determine the total energy dissipated in the resistor and the total distance the rod travels, and explain why the rod never quite stops in finite time.