# Homework Help: Generators (know r, l, B, angular speed of coil) how to find peak EMF?

1. Apr 12, 2005

### michaelw

The coil of a generator has a radius of 0.14 m. When this coil is unwound, the wire from which it is made has a length of 5.7 m. The magnetic field of the generator is 0.20 T, and the coil rotates at an angular speed of 25 rad/s. What is the peak emf of this generator?

Please help me get started on thsi one :)

2. Apr 13, 2005

### vaxopy

i had to do a similar question..
cant remember how i did it though >_<

3. Apr 14, 2005

### ramollari

Knowing the wire length and the loop radius you can determine both loop area A and number of loops N.

Given: $$r = 0.14m, L = 5.7m, B = 0.2T, \omega = 25rad/s$$

$$N = \frac{L}{circumference} = \frac{L}{2\pi r}$$

$$A = \pi r^2$$

$$Emf_{peak} = \omega NBA = \frac{1}{2}\omega LrB$$.

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