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**1. Homework Statement**

A loop of wire is at the edge of a region of space containing a uniform magnetic field B. The plane of the loop is perpendicular to the magnetic field. Now the loop is pulled out of this region in such a way that the area A of the coil inside the magnetic field region is decreasing at the constant rate . That is, [tex]\frac{dA}{dt} = -c[/tex] , with c >0 .

The induced emf in the loop is measured to be V. What is the magnitude B of the magnetic field that the loop was in?

Express your answer in terms of some or all of the variables A ,c , and V.

**2. Homework Equations**

[tex]\epsilon = | \frac{d\Phi_m}{dt} |[/tex]

[tex]\Phi_m = AB[/tex]

[tex]\epsilon = lvB[/tex]

**3. The Attempt at a Solution**

I get these three hints:

Hint 1. The formula for the magnetic flux through a loop

Hint 2. How to take the derivative of the product of two functions

Hint 3. The formula for the emf induced in a loop (Faraday's law)

So I know [tex]B = \frac{\Phi_m}{A}[/tex], would I just find the derivative of that?

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