# Total electrical resistance flux

1. Nov 30, 2009

### yitriana

1. The problem statement, all variables and given/known data
The circular wire loop has 10 turns and a radius of 1.0 cm. The total electrical resistance of the 10 turn loop is 0.10 Ω. The magnitude of the magnetic field due to the solenoid near the wire loop at t = 0 s is 0.002 T. The current through the solenoid doubles between t = 2 s and t = 4 s.

What is magnitude of the rate-of change of the magnetic flux through the wire loop at t = 3 s?

2. Relevant equations
flux = NBA where N is number of turns of wire, B is magnetic field, A is area traversed by one loop

E = IR where E is induced emf on the wire

3. The attempt at a solution

I have calculated the flux accurately 6.28E-6 Wb, but I am having a lot of difficulty with the bolded question. I can't figure out how to manipulate the equations because I don't know the initial current, and I don't know the final magnetic field and I just can't simplify anything.

2. Dec 1, 2009

### kuruman

Re: Flux

How is the magnetic flux related to the current in the solenoid? By this I mean, is it directly proportional, inversely proportional, goes as the square of the current or what? If you can answer this question, then you can figure out by what factor the flux changes from t = 2 to t =3 s and then all you have to do is multiply the 6.28e-6 Wb by that factor to find the flux. Unless you have a figure that shows otherwise, you may assume that the current changes linearly with time.