# Homework Help: Electromagnetic problem

1. Feb 26, 2016

### IndyKuma

1. The problem statement, all variables and given/known data
A rectangle circuit which has a resistor R and has a size l*w. The circuit is moving away from an infinite long wire which has a current i moving up along the wire with velocity v. Find the current moving in the resistor's side which far from the wire r. Here's the figure of the problem. http://imgur.com/RcAbgVN

2. Relevant equations
Maybe Faraday's Law? Like, Φ = ∫ B ⋅ dA and ε = -dλ/dt .

3. The attempt at a solution
I found that my answer is -μ0ilv/2πr. But I'm not sure about it.

Last edited: Feb 26, 2016
2. Feb 27, 2016

### rude man

I get a different answer, involving all the given parameters.
When dealing with moving media such as this loop, use the Blv law rather than Faraday's law. The latter can lead to difficulties.
The Blv law simply states that the voltage induced across a wire (for example) of length l moving at speed v and at right angles to a B field is emf = Blv. In vector form, emf = B (l x v).

In this case you have two lengths inducing differing emf's. Hint: what happens if you connect two batteries of differing voltages + to + (or - to -)?