physics : class12 Potentiometer Working : Potentiometer : Current Electricity MCQ Questions and Answers
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Potentiometer Working
MCQ questions and answers.
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MCQ Questions
1. What is the basic principle of a potentiometer?
A.
Potential drop is proportional to the length of a uniform wire carrying constant current
B.
Resistance is inversely proportional to the length of a wire
C.
Current is proportional to the resistance of a wire
D.
Magnetic field is proportional to the length of a wire
Correct Answer:
Potential drop is proportional to the length of a uniform wire carrying constant current
Explanation:
A potentiometer works on the principle that, for a uniform wire carrying constant current, the potential drop across the wire is directly proportional to its length.
2. Which device is used to locate the null point on the potentiometer wire?
A.
A galvanometer with a jockey
B.
A voltmeter only
C.
An ammeter only
D.
A rheostat without a galvanometer
Correct Answer:
A galvanometer with a jockey
Explanation:
The jockey makes contact at different points of the potentiometer wire, while the galvanometer indicates the null point by showing zero deflection.
3. What does zero deflection in the galvanometer indicate during potentiometer operation?
A.
The potential difference between the compared points is zero
B.
The current in the potentiometer wire is maximum
C.
The resistance of the wire is zero
D.
The cell has no emf
Correct Answer:
The potential difference between the compared points is zero
Explanation:
At zero galvanometer deflection, no current flows through the galvanometer branch, showing that the potential difference between the cell and the corresponding wire point is balanced.
4. Why is a uniform wire used in a potentiometer?
A.
To provide a uniform potential gradient
B.
To increase the magnetic field around the wire
C.
To make the wire an insulator
D.
To produce alternating current
Correct Answer:
To provide a uniform potential gradient
Explanation:
A uniform wire has constant resistance per unit length, so the potential drop per unit length remains uniform when constant current flows through it.
5. In a potentiometer, the potential gradient is the potential drop per unit
A.
Length of the wire
B.
Mass of the wire
C.
Area of the galvanometer
D.
Time of contact of the jockey
Correct Answer:
Length of the wire
Explanation:
The potential gradient is defined as the potential drop across the potentiometer wire divided by its length.
6. At the balance point of a potentiometer, the emf of the test cell is equal to the
A.
Potential drop across the balancing length of the wire
B.
Current flowing through the galvanometer
C.
Resistance of the jockey
D.
Total resistance of the circuit
Correct Answer:
Potential drop across the balancing length of the wire
Explanation:
At balance, the emf of the test cell equals the potential drop across the length of the potentiometer wire up to the null point.
7. What happens to the galvanometer deflection when the jockey is moved away from the correct null point?
A.
It generally becomes non-zero
B.
It always remains zero
C.
The galvanometer becomes disconnected automatically
D.
The potentiometer wire stops carrying current
Correct Answer:
It generally becomes non-zero
Explanation:
Only at the balance point are the potentials equal. Moving the jockey away from that point creates a potential difference and produces galvanometer deflection.
8. The balancing length in a potentiometer is measured from the
A.
Zero end to the null point
B.
Battery terminal to the galvanometer
C.
Rheostat to the battery
D.
Middle of the wire to the jockey
Correct Answer:
Zero end to the null point
Explanation:
The balancing length is the length of potentiometer wire between the chosen zero end and the point where the galvanometer shows zero deflection.
9. Which component is used to vary the current in the potentiometer wire?
A.
Rheostat
B.
Galvanometer
C.
Jockey
D.
Voltmeter
Correct Answer:
Rheostat
Explanation:
A rheostat changes the current in the primary circuit, thereby adjusting the potential gradient along the potentiometer wire.
10. For a constant current in a uniform potentiometer wire, if the balancing length is doubled, the balanced potential difference becomes
A.
Twice as large
B.
Half as large
C.
Unchanged
D.
Zero
Correct Answer:
Twice as large
Explanation:
Since the potential difference is directly proportional to the balancing length for a uniform wire with constant current, doubling the length doubles the balanced potential difference.