physics : class12 Induction in Straight Conductors : Induced Current : Electromagnetic Induction and Alternating Currents MCQ Questions and Answers
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Induction in Straight Conductors
MCQ questions and answers.
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MCQ Questions
1. A straight conducting rod of length l moves with speed v perpendicular to a uniform magnetic field B. What is the induced emf across its ends?
A.
Bvl
B.
Bv/l
C.
Bl/v
D.
B/(vl)
Correct Answer:
Bvl
Explanation:
For a straight conductor moving perpendicular to a magnetic field, the motional emf is given by E = Bvl.
2. A straight conductor moves parallel to the magnetic field lines. What is the induced emf in the conductor?
A.
Bvl
B.
Bl
C.
Zero
D.
Bv
Correct Answer:
Zero
Explanation:
The induced emf is E = Blv sin theta. For motion parallel to the field, theta is zero and sin zero is zero.
3. A straight conducting rod moves perpendicular to a magnetic field. If its speed is doubled while its length and the magnetic field remain unchanged, the induced emf becomes
A.
Half
B.
Unchanged
C.
Twice
D.
Four times
Correct Answer:
Twice
Explanation:
Since E = Bvl, the induced emf is directly proportional to the speed of the rod.
4. A straight conductor of length 0.5 m moves at 4 m/s perpendicular to a magnetic field of 0.2 T. What is the induced emf?
A.
0.04 V
B.
0.4 V
C.
4 V
D.
40 V
Correct Answer:
0.4 V
Explanation:
Using E = Bvl, E = 0.2 x 4 x 0.5 = 0.4 V.
5. In a moving straight conductor, the direction of induced current is determined by
A.
Ohm's law
B.
Fleming's right-hand rule
C.
The law of reflection
D.
The principle of conservation of mass
Correct Answer:
Fleming's right-hand rule
Explanation:
Fleming's right-hand rule gives the direction of induced current in a conductor moving through a magnetic field.
6. A straight conductor moves through a magnetic field but its circuit is open. What is produced across its ends?
A.
A continuous current only
B.
An induced emf but no continuous current
C.
No potential difference
D.
A permanent magnetic field only
Correct Answer:
An induced emf but no continuous current
Explanation:
Motion through the magnetic field separates charges and produces an emf, but an open circuit does not allow continuous current to flow.
7. For a straight conductor moving in a magnetic field, the induced emf is maximum when the conductor moves
A.
Parallel to the magnetic field
B.
Perpendicular to the magnetic field
C.
At rest in the magnetic field
D.
Along the magnetic field lines
Correct Answer:
Perpendicular to the magnetic field
Explanation:
The motional emf is E = Bvl sin theta, which is maximum when theta is 90 degrees.
8. A straight conductor of length 1 m moves at 3 m/s perpendicular to a magnetic field of 0.5 T. What is the induced emf?
A.
0.5 V
B.
1.0 V
C.
1.5 V
D.
3.0 V
Correct Answer:
1.5 V
Explanation:
Using E = Bvl, E = 0.5 x 3 x 1 = 1.5 V.
9. The ends of a straight conductor moving through a magnetic field become oppositely charged because of the magnetic force on
A.
The neutrons in the conductor
B.
The free charges in the conductor
C.
The atoms of the magnetic field
D.
The insulating material outside the conductor
Correct Answer:
The free charges in the conductor
Explanation:
The magnetic force acts on the moving free charges in the conductor, causing charge separation and producing an induced emf.
10. If the length of a straight moving conductor is reduced to half while its speed and the magnetic field remain unchanged, the induced emf becomes
A.
Twice
B.
Four times
C.
Half
D.
Unchanged
Correct Answer:
Half
Explanation:
Because E = Bvl, the induced emf is directly proportional to the length of the conductor.
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