Homework Help: Magnetic field and direction of motion

1. May 24, 2004

UrbanXrisis

Which two angles between the direction of motion of a wire and a magnetic field can a potential difference be induced across the wire?

1. 0 and 45
2. 0 and 90
3. 45 and 90
4. 45 and 180

2. May 24, 2004

Staff: Mentor

motional EMF

For a motional EMF to be induced across the wire, the wire must have a component of motion perpendicular to the magnetic field.

3. May 24, 2004

UrbanXrisis

So it should be 0 and 90. By how many degrees should two wavelengths be out of phase to produce maxium destructive interference?

4. May 24, 2004

Staff: Mentor

Nope. 0 degrees would be parallel to the magnetic field.
Imagine (better yet, draw) two identical waves, one on top of the other. Have far would you have to slide one over to just cancel the other? (Hint: what fraction of a wavelength?)

5. May 24, 2004

UrbanXrisis

half a wavelength?

6. May 24, 2004

UrbanXrisis

so 180 degrees right?

7. May 24, 2004

Staff: Mentor

You got it! How many degrees is that?

8. May 24, 2004

Staff: Mentor

Right again!

9. May 24, 2004

UrbanXrisis

what if two waves traveling in the same medium interfere to produce a standing wave. What is the phase diference in degrees between the two waves at a node?

10. May 24, 2004

Staff: Mentor

standing waves: nodes and anti-nodes

In a standing wave, there are nodes and anti-nodes. The nodes are the places where you see minimum or no amplitude--which means maximum destructive interference; the anti-nodes are the places with maximum amplitude--thus constructive interference.

11. May 24, 2004

UrbanXrisis

how do you find the phase difference though?

12. May 24, 2004