# Mindblowing electromagnetic induction

Hi, I been practicing for my physics compettiotion as I stumbled upon a difficult problem.I couldn't do I for days so I turned to internet in hope someone can help me.

The idea is as following: You have a frame made of wire and its area is S it rotates with a angular speed of W, in a magnetic field of induction B.The question is : "What's the intensity of the max Electromotive force?"

Thanks for your help! :)

## Answers and Replies

Meir Achuz
Science Advisor
Homework Helper
Gold Member
Why isn't it just WBA?

During the first half time period S vector will be changing from S to -S resulting in a change 2S. This happens in time of pi/W.So the time rate of change of area is 2SW/pi. Since B remains the same during the entire process simply multiplying its magnitude will give you the emf.So the value of emf will be 2BSW/pi.Any way i am not quite sure of this

Thx for the reply. :D I tryed the way u did it and it still doesn't mach the given value for the solution... It creeps me out! But I get over it...

Write down a value for the flux linkage when the coil is at an angle theta to the field and then apply Faradays law.

:
Write down a value for the flux linkage when the coil is at an angle theta to the field and then apply Faradays law.

Ya.I tried using that method also and ended up with the same answer:uhh:

You have to differentiate your equation with respect to t.

I'm in the middle school we haven't learned diferencionals or integrals could you show me how to do it... please?