A very long cylindrical solenoid has a radius of 0.50m and 1000 windings per meter along its length. A circular conducting loop of radius 1.0m encircles the solenoid with the long central axis of the solenoid passing through the center of the loop, and with the area vector of the loop parallel to the solenoid axis. The solenoid initially carries a steady current I, but the current is then reduced to 0 during a 0.1s time interval. If the average emf induced in the loop during that interval is 0.1V, what was the initial current magnitude?

Question

anonymous · Answer

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anonymous · Answer

I was able to determine that$$\large B = \mu_0I \frac{N}{L}=\mu_0 In$$and that$$\large emf=\frac{FL}{q}=\frac{qvBL}{q}=vBL$$But I wasn't sure what to do with that once I got that.

irishboy123 · Answer

connect your first statement, ie $\large B = \mu_0I \frac{N}{L}=\mu_0 In$ to the answer via Faradays Law: $\large \mathcal E = - \dot \Phi$ where $\Phi = B A$

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the trick might be to get your head around the areas first.  the loop is outside the solenoid.  maybe do it first assuming that the loop and the solenoid have the same radius?  then we take it from there...?

this link shows some of the fundamentals, it may or may not help.