Problems calculating Flux Density and other related question...

Hi,

This is my first post and I'm looking for some help - I promise I don't make a habit of first posts like this, but I'm freaking out - freaking out BIG TIME.....

I'm studying Automotive Design and I missed a few lectures which covered this subject matter (gotta work to pay college fees....) - got a paper to be handed in tomorrow and I'm absolutely clueless. So I'm hoping some one can point me in the right direction.

Here's a sample of the questions I've got to answer - any assistance would be greatly appreciated.

Quote:

1. A starter motor when operated passes a current of 200 amps through the armature. The reaction between the magnetic field and the armature creates a force of 10 Newtons on the armature winding. Assuming the armature winding is 0.2 meters long (effective length), calculate the Flux Density

Quote:

2. During the Dwell periods of an ignition system the coil produces a flux of 10 webers. If the radius if the magnetic course is 22mm, calculate the flux density

Quote:

3. A winding on an alternator rotor cuts through a magnetic field of 0.6T and is 0.8 meters long. Calculate the induced EMF in the rotor winding if it is moving at a uniform speed of 20m/s

For Q1 does this sound correct? Quote:

Flux Density= F/(I*L) F=force; I=current (amps); L=Length (mm) - therefore the Flux Density would be 10/(200*0.2) = 0.25 Tesla?

The other two - I just ain't got a clue.

Thanks in advance.