Direction of Current

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[SOLVED] Direction of Current

Homework Statement



I am having problems identifying in which way the induced current for a loop will be.

Code:
A loop is placed in a magnetic field as shown in the figure. 
If the magnitude of the field is decreased, the induced current
 in the loop will be.

[PLAIN]http://capa.fiu.edu/CAPA/brfigs/BRing.jpg[/CENTER][/URL] [Broken]

with the following options:

Code:
A) out of the page.
B) clockwise.
C) into the page.
D) counter clockwise.

Homework Equations



Right Hand Rule

The Attempt at a Solution



Well I tried using the right hand rule. I have learned that the x's represent that the current is flowing into the wire, away from me. So I placing my thumb facing away from me, and my finger curl, and it seems to be going out of the page. Also, how do I know if I should turn counterclockwise or clockwise?​
 
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Answers and Replies

  • #2
Doc Al
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Well I tried using the right hand rule. I have learned that the x's represent that the current is flowing into the wire, away from me.
The x's represent the direction of the magnetic field, which is into the page.
So I placing my thumb facing away from me, and my finger curl, and it seems to be going out of the page. Also, how do I know if I should turn counterclockwise or clockwise?
To use the right hand rule like I do, just make a fist with your thumb pointing up. Like you're making a "thumb's up" gesture.

Here's a picture (look at the right-most hand diagram in the middle): http://www.physics.brocku.ca/faculty/sternin/120/slides/rh-rule.html" [Broken]

But first you must understand Faraday's law and http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/farlaw.html#c2". The induced current always goes in a direction that opposes any change to the flux through the loop.
 
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  • #3
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so it is going out of the page.

I tried the right hand rule, pointing into the "page", made the counter clockwise turn and it would be into the page, and since the induced current goes against the magnetic field.
 
  • #4
Doc Al
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so it is going out of the page.
The current flows in the loop. It's either clockwise or counterclockwise.

I tried the right hand rule, pointing into the "page", made the counter clockwise turn and it would be into the page, and since the induced current goes against the magnetic field.
In what direction is the flux changing? What current is needed to oppose that change?
 
  • #5
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I think I know what you are trying to say. We need the current to go into the page, and using the right hand rule that would be going clockwise. We need a current going outwards to oppose the inward force.
 
  • #6
Doc Al
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I think I know what you are trying to say. We need the current to go into the page, and using the right hand rule that would be going clockwise. We need a current going outwards to oppose the inward force.
No.

In this problem, the field points into the page and is decreasing. Therefore the induced current will act in such a way as to increase the field into the page. Which direction of current will produce a field that points into the page?
 
  • #7
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it will point in the direction of the field to keep it constant., the diagram in hyperphysics also shows an arrow pointing down, which must mean, clockwise.
 
  • #8
Doc Al
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it will point in the direction of the field to keep it constant., the diagram in hyperphysics also shows an arrow pointing down, which must mean, clockwise.
Careful with how you describe things. The current does not point in the direction of the field. You need a current that creates a field pointing into the page. Using the right hand rule, a clockwise current is needed to generate such a field.
 
  • #9
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oh, I thought the current was the one points, we were trying to find a current that created a field pointing inwards. Thank you for your help and patience.
 

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