# HELP Induced Voltage question

1. Jun 7, 2006

### Trista

HELP!! Induced Voltage question

Here it is: Coil has 10 turns and shaped in an elipse (A = pie ab), having a major axis of 10 cm (10 X 10^-2 m) and minor axis 4 cm (4 X 10^-2m). Coil rotates 100 rpm in a region in which the magnitude of the Earth's magnetic field is 55 microT. What is max voltage induced in the coil if the axis of rotation of the coil is along its major axis and aligned
a) Perpendicular to earth's magnetic field or
b) parallel

So, I figure my equation should be Emax = NBA omega sin omega t

Then, I figure my area to be: A = pi ((10 X 4)x10^-2 m^2)) = 1.26 m^2
and Omega = 2 pi(rpm / 60) -> 2 pi (100 / 60) = 10.47 rad/s

My equation then looks like this:
10(55X10^-6 T)(1.26 m^2)10.47 rad/s sin 10.47 rad/s t
But it doesn't come out right AND I don't know what t would be, as its not mentioned. a) is supposed to be 18.1 micro V and b) is 0, I suppose becuase it is parallel, no magnetic field is hitting it when parallel, right?

2. Jun 7, 2006

### Trista

hahhaahaha, I got it... I needed to fix my area. S/B (4 cm / 2)(10 cm / 2) = 10 cm... got my answer, thanks anyway