# Emf and coils

1. Feb 19, 2008

### buckeyes

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

In each of two coils the rate of change of the magnetic flux in a single loop is the same. The emf induced in coil 1, which has 200 loops, is 2.67 V. The emf induced in coil 2 is 3.78 V. How many loops does coil 2 have?

2. Relevant equations

E=-N(delta Phi/delta t)

3. The attempt at a solution

i tried setting E+N=E+N because the magnetic flux is the same but that was wrong

2. Feb 19, 2008

### blochwave

F=d(phi)/dt for ease of writing and I always use V if I'm not using the little epsilon for emf

So you got V1+N1*F=V2+N2*F

you can't just get rid of F like you did. Note that you're actually given enough information to SOLVE for F directly just using the equation you were given, then use it to find N

3. Feb 19, 2008

### buckeyes

i'm confused what equation do i use to find F? i have no time so how can I use that equation?

4. Feb 19, 2008

### blochwave

The equation that you just typed in the relevant equations section. For coil 1 you're given N and E, so certainly you can find the change in flux, then just use that same number for coil 2's E to find N

5. Feb 19, 2008

### buckeyes

i got 202.67 for the change in flux of the first coil and .01865 for N of the second coil. that doesn't seem like it is right. is it?

6. Feb 19, 2008

### blochwave

Nope, for coil 1, you have this equation

E=-N(delta Phi/delta t)

You're given E=2.67, and N=200, so you can solve for dphi/dt, which is gonna be 2.67/200, and a pretty small number

7. Feb 19, 2008

### buckeyes

ok then 283.15 turns?

Last edited: Feb 19, 2008