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## Homework Statement

The figure below shows a short coil which is coaxial with a very long solenoid (you may approximate it as infinite.)

Coil: Has 120 turns of radius 1.8 cm and resistance 5.8 . It is not attached to anything.

Solenoid: Has 22700 turns/m and a radius of 1.6 cm. It receives an external current (source not shown).

**a.)**The magnetic field across the coil's entire cross-sectional area (as caused by the solenoid) at any given time: ?

**If the current supplied to the solenoid drops at a constant rate from 1.5 A to zero in in a time interval Δt = 25 ms, What are the magnitudes of the emf and current induced in the coil during this time interval?**

b.)

b.)

**c.)**What is the mutual inductance of this solenoid/coil system?

## Homework Equations

Mutual inductance of coil 2 with respect to coil 1 = M

_{12}= ( N

_{2}* flux

_{12}) / I

_{1}

Mutual-induced emf by 1 on 2 = ε

_{2}= - M * d/(dt) * I

_{1}

B

_{solenoid}= μ

_{o}NI/l

flux = integral of B dot dA

## The Attempt at a Solution

For part (a):

Is a non-zero constant inside the solenoid and zero everywhere else?

For part (c):

I get the mutual inductance, M, is equal to ( μ

_{o}* N

_{1}* N

_{2}* Area ) / length, however I'm not given a length.

## Homework Statement

## Homework Equations

## The Attempt at a Solution

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