Question on lenz law-HSC (1 Viewer)

[jeffwu95]

This is MC 2010 paper the answer says it is D but wouldnt it be C because as an increasing current flows from the outer ring, this would cause a magnetic field into the page between the rings, by lenz law wouldnt a magnetic field have to be induced upwards from the inner ring and thus using the right hand rule for a magnetic field to go outside the page an increasing clockwise current would be formed

 

[tomp1612]

when the current goes through the outer ring it produces a changing magnetic field, this induces the current in the outer ring to flow anti clockwise cause the current is the opposing force which created it

 

[barbernator]

its D

 

[jeffwu95]

alright can you explain bro

 

[unLimitieDx]

Thats correct. As you stated by lenz's law the direction of the induced current will oppose the change that caused it i.e induced a magnetic field upwards .
Hence the only possible answer that will produce a magnetic field upwards is either B or D, the anticlockwise direction (Right hand grip rule). Since the outer ring is increasing current then the inner must also increase current to counteract it there D

 

[tomp1612]

Thats correct. As you stated by lenz's law the direction of the induced current will oppose the change that caused it i.e induced a magnetic field upwards .
Hence the only possible answer that will produce a magnetic field upwards is either B or D, the anticlockwise direction (Right hand grip rule). Since the outer ring is increasing current then the inner must also increase current to counteract it there D

would my explanation be right??

 

[unLimitieDx]

when the current goes through the outer ring it produces a changing magnetic field, this induces the current in the outer ring to flow anti clockwise cause the current is the opposing force which created it

The first half is right but i dont think its really force that was created but rather magnetic field lines.

 

[tomp1612]

also I was just thinking about it, it is sort of like the magnet falling through a copper tube creating an eddy current

 

[Fizzy_Cyst]

Shit question.
It says increasing current -- induced current depends on the RATE at which flux changes. If current increases at a steady RATE, induced current would be constant. If current INCREASES at a DECREASING rate, then the answer will be different..

For direction, use RHG rule. Current is going clockwise, which creates mag field into page inside ring. Seeing as changing mag field is into page, the current in inner ring will be in such a direction to oppose the change, using RHG rule, this is flux out of page, hence anti-clockwise current.

 

[RishBonjour]

I always do these questions by thinking of a magnet with north and south pole from the side. Then apply lenz' law and you get your answer as D

 

[RishBonjour]

when the current goes through the outer ring it produces a changing magnetic field, this induces the current in the outer ring to flow anti clockwise cause the current is the opposing force which created it

not too sure about that :/

 

[someth1ng]

Shit question.
It says increasing current -- induced current depends on the RATE at which flux changes. If current increases at a steady RATE, induced current would be constant. If current INCREASES at a DECREASING rate, then the answer will be different..

For direction, use RHG rule. Current is going clockwise, which creates mag field into page inside ring. Seeing as changing mag field is into page, the current in inner ring will be in such a direction to oppose the change, using RHG rule, this is flux out of page, hence anti-clockwise current.

+1

That is exactly what I thought when I was looking at this question.