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Electromagnetic Induction Worksheet
By the end you will: use Faraday's and Lenz's laws to predict the size and direction of an induced current.
A. Explore with the simulation
Move the magnet in and out of the coil. Fill in what the galvanometer does.
What the magnet does Needle Moves into the coil Rests inside the coil Moves out of the coil Moves in faster Move the magnet at the same speed with 50, 100 and 200 turns. How does the emf change?
Push the north pole in. Which pole forms on the coil's near end? Does it attract or repel the magnet?
B. Calculate
The flux through each turn of a 200-turn coil rises from 1 mWb to 4 mWb in 0.05 s. Find the emf.
That coil has a resistance of 6 Ω. What current flows?
A 1 m axle of a train moves at 30 m/s through a vertical field of 4 × 10⁻⁵ T. Find the emf across it.
C. Think it through
Explain why Lenz's law is a consequence of conservation of energy.
Answer key (for teachers and parents)
- Moving in: swings one way · Still inside: zero · Moving out: swings the other way · Faster: swings further.
- It doubles each time the turns double: emf ∝ N.
- A north pole, which repels the incoming magnet: Lenz's law.
- ε = N ΔΦ ÷ Δt = 200 × 0.003 ÷ 0.05 = 12 V.
- I = 12 ÷ 6 = 2 A.
- ε = B l v = 4 × 10⁻⁵ × 1 × 30 = 1.2 × 10⁻³ V (1.2 mV).
- If the induced current helped the motion, the magnet would speed up by itself and make energy from nothing. Opposing it means you must do work, which becomes electrical energy.
Free to print and share for teaching. Made with the interactive simulation at jugnix.com/simulations/electromagnetic-induction.