## 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.

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
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
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?
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.