# My teacher hasnt been in and Im trying to self teach this topic. Can

1. Nov 30, 2005

### KatieKangaroo

My teacher hasnt been in and Im trying to self teach this topic. Can anyone help me with this question, its probably quite simple but Im really stuck
A flat circular coil of mean diameter 3.0cm has 500 turns and is situated so that the plane of the coil is perpendicular to a uniform magnetic field of flux density 20mT. The intensity of the field is reduced to zero and then increased to 20mT in the opposite direction at the same steady rate throughout. Calculate the EMF induced in the coil if the whole operation takes 60ms.
Thanks in advance for any help.

Also: if the EMF is at its peak, is the current also at its peak?

2. Nov 30, 2005

### El Hombre Invisible

Just use Faraday's law:

$$EMF = -N\frac{\Delta\phi}{\Delta t}$$

You have the magnetic flux density, so flux = density * area. You know the change in magnetic flux (+20mT to -20mT) and you know how long it took (60 ms). N is the number of coils.

Ohm's law is V = iR, so yes: voltage (EMF) is proportional to current.

Last edited: Nov 30, 2005