Induced Current and Magnetic Fields

[d4v3]

Homework Statement

Hey everyone,
I'm studying for a final and have been having difficulty determining induced magnetic field and current direction. I have a document (link below) with 5 sample problems. I answered them all, and put my reasoning for the answers there in italics. Would someone be kind enough to tell me if my answers are correct, and whether or not the process by which I arrived at them is sound? I would greatly appreciate it.

Homework Equations

B=uI/2(pi)r
B=uIN/l
Flux=BAcos(theta)
Vind = N(delta flux)/(delta time)

The Attempt at a Solution

I've put my answers and thought processes in italics on the following document:

http://db.tt/AjJeHK1

 

[Liquidxlax]

1. If the B-field is into the page, the induced B-field would be the opposite to the original field. The induced field would be less than the original. knowing the direction of the B-field use the RHR to find the induced current.

2. looks right

3. The exact same as 2 just different orientation. 2 is right but 3 is not

4. brain fart sorry

5. brain fart sorry

 

[d4v3]

I think maybe I was approaching this the wrong way.

So, on number 2, the current in the wire produces a B original. Then this B original produces a current in the loop. And that current in the loop then produces a B induced?

Before I was going B original to B induced to I induced. I don't know why I find this so confusing. But I really appreciate your help.

Thanks in advance.

 

[Liquidxlax]

I think maybe I was approaching this the wrong way.

So, on number 2, the current in the wire produces a B original. Then this B original produces a current in the loop. And that current in the loop then produces a B induced?

Before I was going B original to B induced to I induced. I don't know why I find this so confusing. But I really appreciate your help.

Thanks in advance.

it usually doesn't matter whether you find the B-field or the induced current. I always found it easier to find the current first, and knowing induced B-field always opposes the original magnetic field

 

[d4v3]

I think I'm on the edge of understanding something here. :) Thanks for your help so far, Liquidxlax.


Would anyone be willing to take a look at the 4th and 5th ones (or all 5 if you have the time) on the document I linked and tell me how far off the mark I am on those? Greatly appreciated.