# Question on Electromagnetism. Specifically to do with speed of an object in a field.

## Homework Statement

Problem is http://imgur.com/bQIFJ

## Homework Equations

I presume F=BIl and E=Blu.

## The Attempt at a Solution

Not very well. I don't really understand how to start the question so if I could get some nudges in the right direction that'd be great. I'm not sure how the speed of the van comes into play here. I gather that I'll have to work out V once for the 38uT field density and then again for the 42uT and get the difference.

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You can find it using E= Bul

I don't think the question has enough information. A loop of wire will not produce any output voltage unless the field is varying. To calculate the output you need the rate at which the field is varying. Vehicle speed plus the two field strengths is not enough to establish the rate of change of the field.

The equation you need is V = - N d(phi)/dt

Do you have a picture/drawing of what this "detector" looks like?