# Homework Help: Average induced voltage

1. Jul 25, 2011

### dumbperson

1. The problem statement, all variables and given/known data

A coil with 10 windings(radius 0,07m) is inside a homogenous magnetic(B=0,050T) field, it makes an angle of 90 degrees with the field lines so the magnetic flux is at it's max. Over a period of 0,050 seconds it gets turned by 180 degrees, what is the average induced voltage?

2. Relevant equations

phi=B*A
Uinduced=-N* dphi/dt

3. The attempt at a solution
The area is 0.07²*pi= 0,015393804 m²
So the magnetic flux in the situation before the turning is 0,015393804*0,050=0,0007696902 Wb
(I dont normally write numbers like this)
After it turns, this is the part i am unsure about, is the magnetic flux now -0,0007696902?
because phi=B*cos(180)*A
so the difference in magnetic flux is -2*(0,0007696902)
Then Uinduced = -10 * (-2*(0,0007696902))/0.050 = 0,31 volts. Is this correct?

I am verry sorry for my english. Thank you!

2. Jul 25, 2011

### dumbperson

Anyone? :-)

3. Jul 25, 2011

### Redbelly98

Staff Emeritus
Welcome to Physics Forums.

Yes, that looks good. I didn't check your arithmetic, but your procedure and reasoning are correct. The flux simply changes sign (+ to -) when the coil is flipped 180 degrees, so the change in flux is 2x the value of the flux.

4. Jul 25, 2011

### dumbperson

Thank you very much !

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