Originally Posted by

**JBswe** Hiya need a little help with this please

The Magnetic flow; M, through a rektangular coil with the area A kan be discribled with M=B*Acos(100pi*T) where B is the magnetic flows density. when the coil rotates - it has 50 rotations per second - inducing a AC current that gives dm/dt. find the amplitude of the AC if its magnetic flows density B=150 mT and the area A=2.5 dm^2

I think i need to derv M=B*Acos(100pi*T) Mr F says: Don't think, know. You have obviously studied induced E.M.F. and Faraday's Law ......

and then put in the numbers but am unsure how do derv this. maybe somthing like M=B*-Asin(100pi*T)+100 ?

if anyone could give me a hand i would be thankful.