1. Mar 24, 2004

### tandoorichicken

Please tell me if this is right:

A coil contains 100 turns of wire in a loop 15cm in diameter. The loop is placed between the poles of a large electromagnet B= 1.0 T, with the plane of the loop perpendicular to the field. If the magnetic field is steadily reduced from 1.0 T to 0 in 16 seconds, is the emf in the coil = 0?

2. Mar 24, 2004

### Chen

I can tell you that it's definitely not 0, not in the first 16 seconds that is.

$$\epsilon ' = \frac{d\phi B}{dt} = \frac{dBS}{dt}$$
S, the area, stays constant but B, the magnetic field, reduces constantly. So the magnetic flux through the coil changes and therefore there is EMF in it.