A square loop of wire with a small resistance is moved with constant speed from

Question

A square loop of wire with a small resistance is moved with constant speed from a field free region into a region of uniform B field (B is constant in time) and then back into a field free region to the left ???????? ???????? ???????? For each statement select T True, F False. (If the first is T and the rest F, enter TFFFF.) A) Upon leaving the field, a clockwise current flows in the loop B) When leaving the field the coil experiences a magnetic force to the right C) While the loop is entirely in the field, the emf in the loop is zero D) Upon entering the field, a clockwise current fiows in the loop E) When entering the field the coil experiences a magnetic force to the left

Explanation / Answer

A)True.
When the loop leaves the magnetic field, the magnetic field in the loop decreases and the induced current tries to reduce this effect (Faraday's law states that the induced current opposes the changes in the magnetic field).
Since the magnetic field is reducing in the wire loop, the direction of the current generated will be in such a way that the magnetic field generated will have the same direction as that of the existing field.
The current should be in the clockwise direction to produce a magnetic field directed into the plane of the paper.
B) True
The magnetic force experienced will be to the right.
When the coil leaves the magnetic field, the direction of the induced current will be clockwise. Only the left part of the coil is in the magnetic field and the current is flowing in the downward direction through that part of the wire.
Using Fleming's left-hand rule, the direction of forefinger along the direction of the magnetic field(into the paper), the middle finger along the direction of the current and then the extended thumb gives the direction of the magnetic force.
C) Ture
While the loop is inside the magnetic field, the induced emf is zero,
The induced emf is generated when there is a change in flux. When the loop is inside the constant magnetic field, the magnetic flux is also constant.
The rate of change of magnetic flux is zero.
D) False
Upon entering the field, an anticlockwise current flows in the loop.
The magnetic field is increasing in the wire loop, so the induced emf will produce a current in such a way that it will oppose the increase in magnetic field.
The current generated in the coil should be in the anticlockwise direction to produce a magnetic field along the outward direction.
E) Ture
When entering the field the wire loop experiences a magnetic force in the left direction.
Only the rightmost part of the coil experience the magnetic force. Using Fleming's left-hand rule we can see that the magnetic force is directed to the left.
Ans: TTTFT

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