jtbteddy
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Name:  ImageUploadedByStudent Room1390428984.499444.jpg
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Size:  164.7 KB i could use flemings left hand rule to find the direction of the current, since i know that the magnetic field is into the page, but ehat about the force/motion? I dont know where to point my thumb:/


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jtbteddy
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The MS For it says:

Direction of current
Position 1 = Q to P / anticlockwise / to the left } (1)
Position 3 = P to Q / clockwise / to the right } [both needed; arrows added to diagram may give current directions at 1 & 3]
[8]
Position 2 = no current (1)


So.. Working backwards I know that the force acting on position 1 is down.. And the force on position 3 is up, but where has this data come from?


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minnigayuen
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I'm confused, shouldn't you use Fleming's Right-Hand Rule, because you're inducing a current through motion?
Therefore i thought at position 1, the current would go clockwise, and at position 3, the current would go anticlockwise - the mark scheme befuddles me
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Stonebridge
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(Original post by jtbteddy)
Name:  ImageUploadedByStudent Room1390428984.499444.jpg
Views: 193
Size:  164.7 KB i could use flemings left hand rule to find the direction of the current, since i know that the magnetic field is into the page, but ehat about the force/motion? I dont know where to point my thumb:/


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It's not Left Hand Rule it's Right Hand Rule because you are being asked about the induced emf and current.

Thumb - motion
First finger - field
Centre finger - induced emf or current.

Do this for the side of the rectangle in the field and you will get the answers in the mark scheme.

R to Q (anticlockwise) in the 1st position
S to P (clockwise) in the 3rd position.

In the 2nd position you have both at the same time and they cancel out.
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jtbteddy
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(Original post by Stonebridge)
It's not Left Hand Rule it's Right Hand Rule because you are being asked about the induced emf and current.

Thumb - motion
First finger - field
Centre finger - induced emf or current.

Do this for the side of the rectangle in the field and you will get the answers in the mark scheme.

R to Q (anticlockwise) in the 1st position
S to P (clockwise) in the 3rd position.

In the 2nd position you have both at the same time and they cancel out.


I dint understand, the rectangle is moving from left to right .. So if i point my thumb tot he left, and the first finger into the page, my middle finger points upwards:/ could you please explain it?


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jtbteddy
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(Original post by minnigayuen)
I'm confused, shouldn't you use Fleming's Right-Hand Rule, because you're inducing a current through motion?
Therefore i thought at position 1, the current would go clockwise, and at position 3, the current would go anticlockwise - the mark scheme befuddles me
Im so confused so stressful


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krisshP
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(Original post by jtbteddy)
I dint understand, the rectangle is moving from left to right .. So if i point my thumb tot he left, and the first finger into the page, my middle finger points upwards:/ could you please explain it?


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The movement arrow is tithe right.
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Stonebridge
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(Original post by jtbteddy)
I dint understand, the rectangle is moving from left to right .. So if i point my thumb tot he left, and the first finger into the page, my middle finger points upwards:/ could you please explain it?


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That's correct.
So it means the emf in the coil in position one, for example, is in the wire on the right of the rectangle because that is the one in the magnetic field. The emf is in the upwards direction which is in the wire RQ and acts upwards. This moves current anticlockwise round the rectangle. R>Q>P>S
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minnigayuen
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(Original post by Stonebridge)
It's not Left Hand Rule it's Right Hand Rule because you are being asked about the induced emf and current.

Thumb - motion
First finger - field
Centre finger - induced emf or current.

Do this for the side of the rectangle in the field and you will get the answers in the mark scheme.

R to Q (anticlockwise) in the 1st position
S to P (clockwise) in the 3rd position.

In the 2nd position you have both at the same time and they cancel out.
So in position 3, shouldn't my thumb be pointing to the right, as the arrow of motion is to the right?

edit: ah okay, so the current only flows in the side of the rectangle which is in the field, i perform understand now.
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Stonebridge
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(Original post by minnigayuen)
So in position 3, shouldn't my thumb be pointing to the right, as the arrow of motion is to the right?

edit: ah okay, so the current only flows in the side of the rectangle which is in the field, i perform understand now.
The emf is only in the one side of the rectangle. The current is pushed round the whole circuit just like there was a cell Where the emf is.
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jtbteddy
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(Original post by Stonebridge)
The emf is only in the one side of the rectangle. The current is pushed round the whole circuit just like there was a cell Where the emf is.
Okay, got it now! Thank you veryvery much!

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