IIT JEE , AIEEE Forum - Physics , Magnetism

jatinpreet

Please explain How to apply lenz's law to find the direction of current induced in a loop.I Know that it is induced so as to oppose the change in flux but how does that help in finding the direction of current ???

Please explain in detail as I have not been able to find out how to apply this law in these type of questions ,here direction of current is being asked.

KAB

The magnetic field is into the paper.So the loop should create a magnetic field directing out of the paper.So the direction of current is anticlockwise.

edison

Well according to lenz's law the current is induced in the circuit in such a manner that it opposes the change caused due to external agency.

Keeping this in mind we proceed as below.

Direction of current and magnetic field is given by RIGHT HAND THUMB RULE.

So if we curl the fingers of right hand then if the direction of curled fingers show direction of current then that of thumb shows the magnetic field. And obviously the magnetic field is perpendicular to the plane containing current of the coil or conductor.

Now in the given picture x sign shows that magnetic field is perpendicular and going inside the plane of paper

So direction of current is such that it opposes/resists the change causing it.

Here as the circular wire moves in Right direction the emf is induced because of change in magnetic field.
But remember here change in magnetic field is such that the magnetic flux is decreasing. So current is induced to resist the change in magnetic flux, which means that current is in CLOCKWISE DIRECTION so that it opposes the decrease in magnetic flux and thus due to this induced current the magnetic field due to induced current is also perpendicular to the plane of paper.

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