A2L Item 237

• Description: Identify the effects on a conducting bar resting on rails as a bar magnet is dropped through the circuit.
• Goal: Hone understanding of Faraday's Law
• Source: 283-715 bar with moving magnet
• Keywords: Electromagnetism, Electric Field, Current, Flux, Magnetic Field

---

The question for students:

A conducting bar is placed on a set of horizontal rails. A bar magnet is positioned above the rails with its north pole facing the rails, and is then released. While the magnet falls toward the rails, which of the following statements are true.

1. There is an electric field in the bar
2. There is a current in the bar
3. The bar remains stationary

1. A only
2. B only
3. C only
4. A and B
5. A and C
6. B and C
7. A, B, and C

---

Commentary for teachers:

Answer

(4) As the bar magnet falls, the magnetic flux through the circuit will change. This will cause an E field and current in the conducting bar. The conducting bar will also experience a magnetic force due to the current flowing in the bar.

---