# Faraday's Law of Induction and EMF

1. May 24, 2007

### stryker123

1. The problem statement, all variables and given/known data

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

d[flux] = int[B*dA]

3. The attempt at a solution

I have no idea how to start this. I tried doing some basic problems, but I just do not understand any of it.

2. May 24, 2007

### Staff: Mentor

What's the magnetic field inside a solenoid? What magnetic flux passes through the coil?

3. Oct 30, 2008

### Ithryndil

Never mind, I posted my own thread.

Last edited: Oct 30, 2008
4. Oct 30, 2008

### cepheid

Staff Emeritus
What is the difference between a coil and a solenoid? (I'm asking the question seriously).

5. Oct 30, 2008

### nasu

For this problem:

COIL

Solenoid

In general people may (and will) say "coil" for the second case too.

6. Nov 1, 2008

### wdednam

Did you consider using the mutual inductance of the coil-solenoid system?

I have a theory question for you that might help to get you started on this problem:

What special characteristic of Mutual inductance helps us to quickly and easily solve problems like this?

Good luck,

Wynand.