Question

In the figure, a region with constant (externally produced) magnetic field is shown. A wire loop moves into the magnetic field.

//img.homeworklib.com/questions/b9da6130-ca78-11eb-8c71-8b0cea09251c.gif?x-oss-process=image/resize,w_560

Which of the following is correct? While the loop is moving into the region with the constant external magnetic field, the magnetic field inside the loop due to the induced current in the loop points ...
No magnetic field is induced by the movement of the loop.
... down
... left
... into the page
... right
... up
... out of the page (the answer)

Tries 0/20

Which of the following is correct? While the loop is moving into the region with the constant external magnetic field, the magnetic force on the loop points ...
... right
... up
There is no magnetic force acting on the loop.
... out of the page
... down
... left
... into the page

I need help with the last 2 problems! Please explain as well!

Answer 1

From Faraday's law of induction we know, The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic flux enclosed by the circuit. Here we have a constant magnetic field B acting inside the page. The loop has a constant area A. The magnetic flux through the loop, when it passes the region of constant magnetic field is,

$\phi = \vec{B}.\vec{A} = BA = const. \hspace{16mm} \frac{d\phi}{dt} = 0$

This means no emf is generated along the loop. Hence no induced current and no induced magnetic field is generated.

We know that magnetic force acts on a current carrying loop, which is given by,

$\vec{F} = \int I (\vec{dl} \times \vec{B})$

Here the loop is not carrying any current (I = 0), not real neither induced. Hence magnetic force acting on the loop is zero.