# School of PhysicsLecture Demonstration Manual

## Eb-2 Faraday's Law of Induction

Published: Tuesday 14 March 2006 - Updated: Tuesday 29 March 2011

### Aim

To demonstrate the generation of an EMF in a coil threaded by a changing magnetic field.

### Apparatus

•  Demonstration box galvanometer
•  2 small coils
•  Magnet
•  6V battery, key switch
•  Hook up wire

### Diagrams

Click on pictures to enlarge.

 Faradyas Law of Induction Diagram 1 Faraday's Law of Induction Diagram 2

### Description

1) A coil (A) is connected to the galvanometer set to its second most sensitive scale. A small magnet is brought into the centre of the coil, held stationary there and then withdrawn. The deflections in each case are noted; only relative motion produces a deflection.

2) The magnet is taken away and replaced with the circuit shown below. Coil B must be placed as close to coil A as possible and the sensitivity of the galvanometer increased to maximum.

Deflections are noted on closing or opening the switch but not while there is a steady current in the circuit.

At this stage some lecturers might like to introduce the concept of permeability by placing a thick iron bar so as to thread coils A and B. The deflections are increased on repeating the experiment.