# Homework Help: Electromagnetic Induction

1. Mar 5, 2012

### physgrl

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

A flat coil of wire has an area of 0.010 m2and contains 100 turns. Initially the coil is oriented so that the normal to its surface is parallel to a downward constant magnetic field of 0.2 T. The coil is then rotated clockwise through an angle of 30oin a time of 0.10 s. What is the average induced emf? (Note: the initial emf is zero)

a. 0.50 V

b. 0.45 V

*c. 0.18 V

d. 0.25 V

2. Relevant equations

emf=-Δ$\Phi$B/Δt
$\Phi$B=N*ABcos(θ)

3. The attempt at a solution
emf=-Δ$\Phi$B/Δt
emf=-N*AB(cos(θ1)-cos(θ2))/Δt
emf=-100*0.01m2*.2T(cos(0)-cos(30))/.1s
emf=2.7x10-2V

the answer appears to be .18V...can someone tell me why is this? thanks!

2. Mar 5, 2012

### I like Serena

Hey!

Nope. I can't tell you why that is.
Btw, he answer I get is emf=0.27V, so it seems to me you made a mistake with the power of 10.

The right answer isn't even in there.
Is it possible you made a typo when typing down the problem statement?

Anyway, I believe we've given you an answer like this one a couple of times before.

3. Mar 5, 2012

### physgrl

Last edited by a moderator: May 5, 2017
4. Mar 5, 2012

### I like Serena

So where's this one and its "answer"?

5. Mar 5, 2012

### physgrl

on the first link unit 3>>chapter 14>>lesson 41>> assessments >>answer key >>question 7

6. Mar 5, 2012

### I like Serena

Yep. I see it.
And still no clue why the answer would be wrong.

7. Mar 5, 2012

Oh well :/