Electromagnetic Induction & Faraday's Law
Classroom worksheet · Interactive simulation: https://lkforge.com/tools/physics/electromagnetic-induction/
Name: Date:
Learning objectives
- State Faraday’s law relating EMF to changing flux.
- Apply Lenz’s law to find the induced current’s direction.
- Identify what increases induced EMF.
Variables to change
- Magnet speed
- Number of coil turns
- Magnetic strength
Procedure
- Move a magnet slowly through the coil and note the induced EMF.
- Move it faster and compare.
- Increase the number of coil turns and repeat.
- Hold the magnet still inside the coil and observe.
Observations
Record induced EMF versus magnet speed and number of turns, and note direction changes.
Questions
- State Faraday’s law.
- What happens to the EMF when the magnet moves faster?
- Why is there no EMF when the magnet is held still in the coil?
- What does Lenz’s law say about the induced current’s direction?
- How does adding coil turns change the EMF?
Answer key (instructors)
- 1. The induced EMF equals the rate of change of magnetic flux: EMF = -N·dΦ/dt.
- 2. It increases, because flux changes more rapidly.
- 3. The flux is constant, so dΦ/dt = 0 and no EMF is induced.
- 4. It flows so as to oppose the change in flux that produced it (the minus sign in Faraday’s law).
- 5. EMF scales with the number of turns N — more turns give a larger EMF.
A changing magnetic flux through a coil induces an EMF (Faraday’s law, EMF = -N·dΦ/dt). Faster changes and more turns give larger EMF, and Lenz’s law says the induced current opposes the change — the basis of generators and transformers.