physics : class12 Induction in Solenoids : Induced Current : Electromagnetic Induction and Alternating Currents MCQ Questions and Answers
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Induction in Solenoids
MCQ questions and answers.
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MCQ Questions
1. A changing current in a solenoid produces an induced emf in the same solenoid. This phenomenon is called:
A.
Self-induction
B.
Electrostatic induction
C.
Photoelectric emission
D.
Thermal conduction
Correct Answer:
Self-induction
Explanation:
When the current in a solenoid changes, its magnetic flux changes and an emf is induced in the same solenoid. This is called self-induction.
2. The induced emf in a solenoid is produced when the magnetic flux linked with it:
A.
Remains constant
B.
Changes with time
C.
Becomes zero permanently
D.
Has a fixed direction only
Correct Answer:
Changes with time
Explanation:
According to Faraday's law, an emf is induced in a solenoid when the magnetic flux linked with its turns changes with time.
3. The SI unit of self-inductance of a solenoid is:
A.
Tesla
B.
Weber
C.
Henry
D.
Coulomb
Correct Answer:
Henry
Explanation:
Self-inductance is measured in henry. One henry is the inductance that produces an induced emf of one volt when current changes at one ampere per second.
4. If the current through a solenoid increases, the induced current in the solenoid opposes:
A.
The increase in current
B.
The resistance of the wire
C.
The number of turns
D.
The length of the solenoid
Correct Answer:
The increase in current
Explanation:
By Lenz's law, the induced current opposes the change producing it. Therefore, when current increases, the induced current opposes that increase.
5. The self-induced emf in a solenoid is directly proportional to the rate of change of:
A.
Resistance
B.
Current
C.
Temperature
D.
Wire thickness
Correct Answer:
Current
Explanation:
The self-induced emf is given by E = -L(dI/dt), so its magnitude depends on the rate of change of current in the solenoid.
6. A solenoid has greater self-inductance when it has:
A.
Fewer turns and a shorter length
B.
More turns and a larger cross-sectional area
C.
No turns and a small area
D.
A broken conducting wire
Correct Answer:
More turns and a larger cross-sectional area
Explanation:
The self-inductance of a solenoid increases with the square of the number of turns and with its cross-sectional area.
7. When a battery is suddenly connected to a solenoid, the current does not reach its maximum value instantly because of:
A.
Self-induction
B.
Gravitational induction
C.
Nuclear force
D.
Sound resonance
Correct Answer:
Self-induction
Explanation:
The increasing current produces a self-induced emf that opposes the increase, so the current in the solenoid rises gradually.
8. If the current in a solenoid is made constant, the self-induced emf in it becomes:
A.
Maximum
B.
Zero
C.
Equal to the current
D.
Infinite
Correct Answer:
Zero
Explanation:
For constant current, the rate of change of current is zero. Hence, the self-induced emf, E = -L(dI/dt), is zero.
9. The direction of induced current in a solenoid is determined by:
A.
Lenz's law
B.
Ohm's law
C.
Coulomb's law
D.
The law of reflection
Correct Answer:
Lenz's law
Explanation:
Lenz's law states that the induced current flows in a direction that opposes the change in magnetic flux through the solenoid.
10. Two nearby solenoids are placed close together. A changing current in the first solenoid induces an emf in the second solenoid. This is called:
A.
Mutual induction
B.
Self-heating
C.
Electrostatic shielding
D.
Magnetic saturation
Correct Answer:
Mutual induction
Explanation:
A changing current in one solenoid changes the magnetic flux linked with a nearby second solenoid, inducing an emf in it. This is mutual induction.
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