# Homework Help: A few Electromagnetic questions

1. Apr 8, 2007

### Plasma

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

http://i12.photobucket.com/albums/a234/Xuxyz/battery.jpg" [Broken]

(a) i. Using the information in the graph, determine the potential difference Vo across the resistor immediately after the switch is closed.

2. Relevant equations
Vo = Io * R

3. The attempt at a solution
I don't know how to find Io using the grap, because as you can see from my link, it doesn't intersect at a specific point.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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

http://i12.photobucket.com/albums/a234/Xuxyz/04-08-2007015444PM.jpg" [Broken]

I only need help on part f

2. Relevant equations

I don't know.

3. The attempt at a solution

None, sorry. I don't have a clue.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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

http://i12.photobucket.com/albums/a234/Xuxyz/04-08-2007020007PM.jpg" [Broken]

Only part D

2. Relevant equations

EMF = vBD
I = vBD / R

~~~~~

I know this is a lot, but I would appreciate any and all help.

Last edited by a moderator: May 2, 2017
2. Apr 8, 2007

### robb_

For number 1, it looks to me like the graph shows a current of about 9.5 A??

*For your second question, what is happening as the loop is moving away from the wire?*

3. Apr 8, 2007

### Plasma

It's actually slightly below 9.5 A

The Magnetic field strength is decreasing.

4. Apr 8, 2007

### robb_

1. Okay, slightly less than 9.5 A.
2. So if the field strength is decreasing, what about the flux?

5. Apr 8, 2007

### Plasma

But I need an actual number for the equation to work.

The flux would be decreasing, too?

6. Apr 8, 2007

### robb_

1. You must use your eyeball.
2. Yes, the flux is decreasing, good. From this, can you tell me which direction is the induced current.

7. Apr 8, 2007

### Plasma

I don't need to know the direction of the current, I need to figure out what it's equal to.

8. Apr 8, 2007

### robb_

Well, I thought you might want to learn what is happening.
What does a changing flux produce?

9. Apr 8, 2007

### Plasma

The induced current is counterclockwise.

10. Apr 8, 2007

### robb_

Very good.

11. Apr 8, 2007

### Plasma

12. Apr 8, 2007

### robb_

A changing flux induces an emf around the circuit. Find out the relationship between this emf and other physical quantities.

13. Apr 8, 2007

### Plasma

EMF = the derivative of flux vs time.

14. Apr 9, 2007

### robb_

So can you quantify how the flux changes?