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7
MCQ (Multiple Correct Answer)

A metal plate is getting heated. It can be because

A
a direct current is passing through the plate
B
it is placed in a time varying magnetic field
C
it is placed in a space varying magnetic field, but does not vary with time
D
a current (either direct or alternating) is passing through the plate
8
MCQ (Multiple Correct Answer)

An emf is produced in a coil, which is not connected to an external voltage source. This can be due to

A
the coil being in a time varying magnetic field
B
the coil moving in a time varying magnetic field
C
the coil moving in a constant magnetic field
D
the coil is stationary in external spatially varying magnetic field, which does not change with time
9
MCQ (Multiple Correct Answer)

The mutual inductance $M_{12}$ of coil 1 with respect to coil 2

A
increases when they are brought nearer
B
depends on the current passing through the coils
C
increases when one of them is rotated about an axis
D
is the same as $M_{21}$ of coil 2 with respect to coil 1
10
MCQ (Multiple Correct Answer)

A circular coil expands radially in a region of magnetic field and no electromotive force is produced in the coil. This can be because

A
the magnetic field is constant
B
the magnetic field is in the same plane as the circular coil and it may or may not vary
C
the magnetic field has a perpendicular (to the plane of the coil) component whose magnitude is decreasing suitably
D
there is a constant magnetic field in the perpendicular (to the plane of the coil) direction
11
Subjective

Consider a magnet surrounded by a wire with an on/off switch $S$ (figure). If the switch is thrown from the off position (open circuit) to the on position (closed circuit), will a current flow in the circuit? Explain.

Explanation

When the switch is thrown from the off position (open circuit) to the on position (closed circuit), then neither $B$, nor $A$ nor the angle between $B$ and $A$ change. Thus, no change in magnetic flux linked with coil occur, hence no electromotive force is produced and consequently no current will flow in the circuit.

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