physics : class12 Potentiometer Principle : Potentiometer : Current Electricity MCQ Questions and Answers
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Potentiometer Principle
MCQ questions and answers.
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MCQ Questions
1. In a potentiometer wire, the potential gradient is defined as the potential drop per unit:
A.
Area
B.
Resistance
C.
Length
D.
Current
Correct Answer:
Length
Explanation:
The potential gradient is the potential drop across the potentiometer wire divided by its length, so it is measured as potential drop per unit length.
2. If the potential gradient of a potentiometer wire is constant, what happens to the potential drop when the balancing length is doubled?
A.
It becomes half
B.
It remains unchanged
C.
It becomes four times
D.
It becomes double
Correct Answer:
It becomes double
Explanation:
Since potential drop is directly proportional to length for a uniform wire, doubling the balancing length doubles the potential drop.
3. At the balance point of a potentiometer, the potential difference being measured is equal to:
A.
The current in the wire
B.
The potential drop across the balancing length
C.
The resistance of the wire
D.
The total current supplied by the cell
Correct Answer:
The potential drop across the balancing length
Explanation:
At balance, the potential difference of the source being measured equals the potential drop along the potentiometer wire up to the null point.
4. The potential drop across a uniform potentiometer wire is 2 V for a length of 4 m. What is the potential gradient?
A.
0.5 V m^-1
B.
2 V m^-1
C.
4 V m^-1
D.
8 V m^-1
Correct Answer:
0.5 V m^-1
Explanation:
Potential gradient equals potential drop divided by length: 2 V / 4 m = 0.5 V m^-1.
5. Why must the potentiometer wire be uniform for its principle to apply directly?
A.
So that its mass remains constant
B.
So that the potential gradient remains constant along its length
C.
So that no current flows through it
D.
So that its temperature becomes zero
Correct Answer:
So that the potential gradient remains constant along its length
Explanation:
A uniform wire has constant resistance per unit length. With constant current, this gives a constant potential drop per unit length.
6. A potentiometer wire has a potential gradient of 0.02 V cm^-1. What potential difference is balanced by a length of 10 cm?
A.
0.02 V
B.
0.2 V
C.
2 V
D.
20 V
Correct Answer:
0.2 V
Explanation:
The balanced potential difference equals potential gradient multiplied by balancing length: 0.02 V cm^-1 × 10 cm = 0.2 V.
7. At the balance point in a potentiometer, the galvanometer shows:
A.
Maximum deflection
B.
Zero deflection
C.
Constant current deflection
D.
Random deflection
Correct Answer:
Zero deflection
Explanation:
At balance, no current flows through the galvanometer because the potential difference between its terminals is zero.
8. If a potential difference V is balanced at length l on a potentiometer wire, the relation between V and l is:
A.
V is proportional to l
B.
V is proportional to 1/l
C.
V is proportional to l^2
D.
V is independent of l
Correct Answer:
V is proportional to l
Explanation:
For a uniform wire carrying constant current, the potential drop increases linearly with length, giving V proportional to l.
9. A 1 V cell balances at a length of 50 cm on a potentiometer wire. At what length will a 2 V cell balance under the same conditions?
A.
25 cm
B.
50 cm
C.
100 cm
D.
150 cm
Correct Answer:
100 cm
Explanation:
Under the same potential gradient, balancing length is directly proportional to potential difference. Therefore, doubling the voltage from 1 V to 2 V doubles the length from 50 cm to 100 cm.
10. The principle of a potentiometer is based on the fact that the potential drop across a uniform wire is proportional to its
A.
length
B.
radius
C.
mass
D.
temperature
Correct Answer:
length
Explanation:
For a uniform potentiometer wire carrying a steady current, the potential gradient is constant, so the potential drop is directly proportional to the length of the wire.