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*In a physics laboratory experiment, a coil with 210 turns enclosing an area of 12.7 cm^2 is rotated during the time interval [tex]3.70 \cdot 10^{−2}[/tex] sfrom a position in which its plane is perpendicular to Earth's magnetic field to one in which its plane is parallel to the field. The magnitude of Earth's magnetic field at the lab location is [tex]5.20 \cdot 10^{−5}[/tex] T.*

**What is the magnitude of the average emf induced in the coil?**

I've already found the total magnitude of the magnetic flux through the coil before and after rotation.

Since the magnitude after rotation is zero, the change in magnetic flux is merely the negative of the initial magnetic flux.

I use the equation [tex]{\cal{E}} = - N \frac{d \Phi_1}{dt} = - N \frac{\Delta \Phi_1}{\Delta t}[/tex].

Plugging in, I get [tex]-\frac{210 \cdot (-1.39 \cdot 10^{-5})}{3.70 \cdot 10^{-2}}[/tex].

The negatives cancel out, leaving me with a positive answer.

But, my answer is wrong.

What happened?

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