1. The problem statement, all variables and given/known data(adsbygoogle = window.adsbygoogle || []).push({});

A coil of 15 turns and radius 10cm surrounds a long solenoid of radius 2cm and 1x10^3 turns/m. The current in the solenoid changes as I = (5A)sin(120t). Find the induced emf in the 15-turn coil as a function of time.

2. Relevant equations

emf = -Nd[flux]/dt

[tex]\Phi = \oint[B*dA][/tex]

3. The attempt at a solution

Edit: I figured out what I was doing wrong. However, I am still puzzled on one aspect of this problem

When I figured out what I did wrong I came up with:

[tex]B = \munI[/tex]

[tex]Emf = \frac{d}{dt}(NBAcos\theta) = \frac{d}{dt}(NBA)[/tex] cos(theta) = 1 in this case

[tex]Therefore:

Emf = NA\mun(I)[/tex] ...and we have I so it's a simple derivative from there

What I don't get is why the .1m radius doesn't really come into play. Unless I missed something or am not thinking here at all, it's not necessary for this problem, other than to tell us the coils are outside the solenoid.

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# Homework Help: Faraday's Law, Induction Help.

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