Eb-2 Faraday's Law of Induction
Published: Tuesday 14 March 2006 - Updated: Tuesday 29 March 2011
To demonstrate the generation of an EMF in a coil threaded by a changing magnetic field.
- Demonstration box galvanometer
- 2 small coils
- 6V battery, key switch
- Hook up wire
Click on pictures to enlarge.
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 A small magnet is brought into the centre of the coil, held stationary there and then withdrawn.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.