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. A potentiometer works on the principle that the potential drop along a uniform wire carrying a steady current is proportional to its:
A.
Length
B.
Mass
C.
Thickness only
D.
Temperature only
Correct Answer:
Length
Explanation:
For a uniform potentiometer wire carrying steady current, the potential drop is directly proportional to the length of the wire.
2. In a potentiometer, the wire should be uniform so that the potential gradient is:
A.
Constant along the wire
B.
Zero at every point
C.
Maximum only at the middle
D.
Different at every point
Correct Answer:
Constant along the wire
Explanation:
A uniform wire has uniform resistance per unit length, so the potential drop per unit length remains constant.
3. The sliding contact used to locate the balance point on a potentiometer wire is called a:
A.
Jockey
B.
Rheostat
C.
Galvanometer
D.
Key
Correct Answer:
Jockey
Explanation:
The jockey is moved along the potentiometer wire to find the point where the galvanometer shows zero deflection.
4. At the balance point of a potentiometer, the galvanometer shows:
A.
Zero deflection
B.
Maximum deflection
C.
Continuous oscillation
D.
A fixed large deflection
Correct Answer:
Zero deflection
Explanation:
At balance, the potential difference across the tested cell equals the potential drop along the corresponding length of the potentiometer wire, so no current flows through the galvanometer.
5. The potential drop per unit length of a potentiometer wire is known as the:
A.
Potential gradient
B.
Terminal voltage
C.
Electric power
D.
Cell constant
Correct Answer:
Potential gradient
Explanation:
Potential gradient is defined as the potential drop per unit length of the potentiometer wire.
6. If the balancing length for a cell is l and the potential gradient is k, the emf of the cell is:
A.
kl
B.
k divided by l
C.
l divided by k
D.
k plus l
Correct Answer:
kl
Explanation:
The emf is equal to the potential drop across the balancing length, so E = k multiplied by l.
7. In a potentiometer circuit, the primary circuit is used to:
A.
Maintain a steady potential gradient along the wire
B.
Measure the resistance of the galvanometer
C.
Increase the emf of the test cell
D.
Produce zero current in the potentiometer wire
Correct Answer:
Maintain a steady potential gradient along the wire
Explanation:
The primary circuit sends steady current through the potentiometer wire, producing the potential gradient required for comparison.
8. When the jockey is moved toward the end of a potentiometer wire, the potential drop from the starting end generally:
A.
Increases
B.
Decreases to zero immediately
C.
Remains unchanged
D.
Becomes independent of wire length
Correct Answer:
Increases
Explanation:
Since the potential drop is proportional to length, moving the jockey farther from the starting end increases the potential drop.
9. At the balance point, the potentiometer measures the emf of a cell because the cell:
A.
Supplies no current to the external circuit connected through the galvanometer
B.
Has no internal resistance
C.
Is completely discharged
D.
Produces maximum current
Correct Answer:
Supplies no current to the external circuit connected through the galvanometer
Explanation:
At balance, no current is drawn from the cell through the galvanometer branch, so the measured potential corresponds to its emf.
10. If the current through a uniform potentiometer wire is increased, its potential gradient will:
A.
Increase
B.
Decrease to zero
C.
Remain exactly unchanged
D.
Become negative
Correct Answer:
Increase
Explanation:
The potential gradient is the potential drop per unit length. Increasing the current increases the potential drop across the wire and therefore increases the gradient.