physics : class12 Conducting Loop : Induced Current : Electromagnetic Induction and Alternating Currents MCQ Questions and Answers
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Conducting Loop
MCQ questions and answers.
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MCQ Questions
1. An induced current is produced in a conducting loop when the magnetic flux through the loop
A.
remains constant
B.
changes with time
C.
is always zero
D.
has a constant value
Correct Answer:
changes with time
Explanation:
According to Faraday's law, a change in magnetic flux through a conducting loop produces an induced electromotive force and hence an induced current.
2. A conducting loop is placed in a uniform magnetic field with its plane perpendicular to the field. If the loop remains stationary and the field is constant, the induced current is
A.
maximum
B.
zero
C.
alternating
D.
infinite
Correct Answer:
zero
Explanation:
The magnetic flux through the stationary loop does not change when the magnetic field is constant, so no induced current is produced.
3. When the north pole of a bar magnet is moved toward a conducting loop, the near face of the loop behaves like a
A.
south pole
B.
north pole
C.
neutral face
D.
magnetic monopole
Correct Answer:
north pole
Explanation:
By Lenz's law, the induced current produces a magnetic field that opposes the approach of the north pole. Therefore, the near face of the loop becomes a north pole.
4. If the magnetic flux through a conducting loop increases, the induced current produces a magnetic field that
A.
supports the increase
B.
opposes the increase
C.
has no direction
D.
always points upward
Correct Answer:
opposes the increase
Explanation:
Lenz's law states that the induced current opposes the change in magnetic flux that produces it.
5. The magnitude of induced emf in a conducting loop depends directly on the rate of change of
A.
magnetic flux
B.
loop resistance only
C.
loop temperature only
D.
wire length only
Correct Answer:
magnetic flux
Explanation:
Faraday's law states that the induced emf is proportional to the rate at which magnetic flux through the conducting loop changes.
6. A conducting loop is moved into a region of magnetic field. During the entry of the loop, the induced current is
A.
produced because the flux changes
B.
zero because the loop is closed
C.
produced only if the loop is made of wood
D.
independent of the magnetic field
Correct Answer:
produced because the flux changes
Explanation:
As the loop enters the magnetic field, the magnetic flux through it changes. This change produces an induced emf and current in the conducting loop.
7. For the same induced emf, increasing the resistance of a conducting loop will make the induced current
A.
larger
B.
smaller
C.
unchanged in every case
D.
infinite
Correct Answer:
smaller
Explanation:
The induced current is given by the induced emf divided by the resistance of the loop. Thus, increasing resistance decreases the induced current for the same emf.
8. If a conducting loop is cut at one point, an induced emf may still exist, but the induced current is
A.
zero because the circuit is open
B.
maximum
C.
equal to the induced emf
D.
always alternating
Correct Answer:
zero because the circuit is open
Explanation:
A cut loop is an open circuit. Even if changing magnetic flux produces an emf, a continuous path for current is absent, so induced current does not flow.
9. A conducting loop is rotated in a magnetic field. An induced current is produced because the rotation changes the
A.
mass of the loop
B.
magnetic flux through the loop
C.
number of electrons in the loop
D.
chemical composition of the loop
Correct Answer:
magnetic flux through the loop
Explanation:
Rotation changes the angle between the loop and the magnetic field, thereby changing the magnetic flux and producing an induced current.
10. The direction of induced current in a conducting loop is determined by
A.
Lenz's law
B.
Ohm's law alone
C.
the mass of the loop
D.
the color of the wire
Correct Answer:
Lenz's law
Explanation:
Lenz's law determines the direction of induced current by stating that the current opposes the change in magnetic flux through the conducting loop.
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