# Uniform Magnetic field in a circular coil

1. Nov 19, 2009

### hitman0097

A 138 turn circular coil has a diameter of 2.00 cm and resistance of 53.0 Ω. The plane of the coil is perpendicular to a uniform magnetic field of magnitude 1.00 T. The direction of the field is suddenly reversed.

a.) Find the total charge that passes through the coil.
b.) If the reversal takes 0.100 s, find the average current in the coil.
c.) Find the average emf in the coil.

I am using stuff for a solenoid is that the same as a circular coil?
l=lenght
n= # of turns per unit length
N=n*l total # of turns
A=π*r^2
Magnetic Flux=B*A (threw one turn)
B=mu_0*n*I (magnetic field inside solenoid)
Inductance=((N*(B*A))/I)=mu_0*n^2*A*l
E=IR

I don't know what to do. Any suggestions ?

2. Nov 19, 2009

### hitman0097

mu_0= 4pi*10^-7

3. Nov 19, 2009

### lubuntu

The questions seem to be listed in the reverse of the sensible order. Indeed you can use the solenoid equations on the circular current loop(this is what a solenoid is). First find the average change in flux over the time period through the coil. That gives you that average EMF, then V=IR gives you the current. Since I= dq/dt you can find then find the total charge through the wire.

Last edited: Nov 19, 2009