How Does the Changing Current in a Solenoid Affect a Coil Within It?

[ttiger2k7]

[SOLVED] EMF problem - Current in Coil

Homework Statement

A small square coil is located inside an ideal solenoid at the center with its plane oriented perpendicular to the axis of the solenoid. The resistance of this coil is 2.00 \Omega and each side is 4.00 cm long. The solenoid has 125 windings per centimeter of length. If the current in the solenoid is increasing at a constant rate of 1.50 A/s, the current in the square coil is:

a) steady at 18.8 \mu A
b) initially equal at 18.8 \mu A but is increasing
c) increasing at 1.50 A/s
d) decreasing at 1.50 A/s
e) zero

Homework Equations

\epsilon=\frac{d\Phi_{B}}{dt}

<br /> \Phi_{B}=BA<br />

The Attempt at a Solution

First, I plugged in what I know for magnetic flux:

\Phi_{B}=BA=B(.04 m^{2})

Then I used that information to plug into the induced emf formula:

And since

B=\frac{N}{L}*i*\mu_{0}

Then

\epsilon=\left|.04 m^{2}*\frac{N}{L}*\mu_{0}*\frac{di}{dt}\right|

where
\frac{di}{dt} is 1.5 A/S
N = (125 *.04 m) = 5

**

My question is, am I going about this the right way? And if so, How do I find L and how can I use that to eventually get to the induced current?

 

[rock.freak667]

Well \frac{N}{L} is the number of turns per unit length. Which is given in the question. (Just convert the units)

When you get the induced emf, use V=IR to find the induced current...

 

[ttiger2k7]

Okay. (I thought L was inductance). I got a value, but how do I know if its increasing/decreasing, or steady?