# Production of electric current

1. Jul 31, 2006

### uwmphysics

In which of the following situations is an electric current not produced?
a. a loop of wire rotates in a steady magnetic field
b. a loop of wire is stationary in a steady magnetic field
c. the magnetic field through the loop is increasing
d. the magnetic field through the loop is decreasing

Ok-I know that if you change hte magnetic field then the flux would change, and therefore produce an electric current, so I think its safe to say that c an d d are both wrong. But I have no clue how the wire's movement/lack of movement in a steady magnetic field would change things....can someone help me understand that?

thank you!

2. Jul 31, 2006

### Andrew Mason

Remember, the flux is the dot product of B and A: $\phi = \vec{B}\cdot\vec{A} = BAcos\theta$

Does this change when the loop is stationary in a stationary field? Does it change when the loop rotates in a stationary B field (ie. the angle between B and A continually changes)?

AM

3. Jul 31, 2006

### borisleprof

Suppose that the magnetic field is vertical upward.
Suppose you have a round loop in a horizontal plane.
Now rotate the loop along an axis wich is horizontal.
What will happen to the flux of the magnetic field through the loop?