Magnetic field and direction of motion

[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

 

[Doc Al]

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.

 

[UrbanXrisis]

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

 

[Doc Al]

So it should be 0 and 90.

Nope. 0 degrees would be parallel to the magnetic field.

By how many degrees should two wavelengths be out of phase to produce maxium destructive interference?

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?)

 

[UrbanXrisis]

half a wavelength?

 

[UrbanXrisis]

so 180 degrees right?

 

[Doc Al]

half a wavelength?

You got it! How many degrees is that?

 

[Doc Al]

so 180 degrees right?

Right again!

 

[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?

 

[Doc Al]

standing waves: nodes and anti-nodes

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?

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.

 

[UrbanXrisis]

how do you find the phase difference though?

 

[Doc Al]

how do you find the phase difference though?

Reread the thread and I'll bet you can figure it out.