physics : class12 Balancing Length : Potentiometer : Current Electricity MCQ Questions and Answers
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Balancing Length
MCQ questions and answers.
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MCQ Questions
1. In a potentiometer, the balancing length is the length of the potentiometer wire at which the galvanometer shows:
A.
Maximum deflection
B.
Zero deflection
C.
Constant deflection
D.
Random deflection
Correct Answer:
Zero deflection
Explanation:
At the balancing length, no current flows through the galvanometer, so it shows zero deflection.
2. If the balancing length for a cell is 60 cm, the potential difference of the cell is proportional to:
A.
30 cm
B.
60 cm
C.
120 cm
D.
1 cm
Correct Answer:
60 cm
Explanation:
For a uniform potentiometer wire, the potential difference is directly proportional to the balancing length.
3. The balancing length in a potentiometer is measured from the:
A.
Positive terminal to the jockey position
B.
Negative terminal to the jockey position
C.
Middle of the wire to the jockey position
D.
Battery terminal to the galvanometer
Correct Answer:
Negative terminal to the jockey position
Explanation:
The balancing length is measured from the end of the potentiometer wire connected to the negative terminal of the driving cell to the null point.
4. For a uniform potentiometer wire, if the potential gradient is 0.02 V/cm and the balancing length is 50 cm, the potential difference is:
A.
0.04 V
B.
0.4 V
C.
1.0 V
D.
2.5 V
Correct Answer:
1.0 V
Explanation:
The potential difference is the product of potential gradient and balancing length: E = 0.02 × 50 = 1.0 V.
5. If the potential difference of a cell increases while the potential gradient remains constant, its balancing length will:
A.
Decrease
B.
Increase
C.
Become zero
D.
Remain unchanged in every case
Correct Answer:
Increase
Explanation:
Since E = k l, the balancing length increases when the cell potential difference increases at constant potential gradient.
6. Two cells have balancing lengths of 40 cm and 80 cm on the same potentiometer wire. The ratio of their potential differences is:
A.
1:1
B.
1:2
C.
2:1
D.
4:1
Correct Answer:
1:2
Explanation:
On the same wire, the potential gradient is the same, so the potential differences are proportional to their balancing lengths: 40:80 = 1:2.
7. A jockey is moved along a potentiometer wire to locate the position where the galvanometer shows zero deflection. This position is called the:
A.
Heating point
B.
Null point
C.
Terminal point
D.
Current point
Correct Answer:
Null point
Explanation:
The position corresponding to zero galvanometer deflection is called the null point, and its distance gives the balancing length.
8. A cell balances at 75 cm on a potentiometer wire. If the potential gradient is 0.01 V/cm, the emf of the cell is:
A.
0.075 V
B.
0.75 V
C.
7.5 V
D.
75 V
Correct Answer:
0.75 V
Explanation:
Using E = k l, the emf is 0.01 × 75 = 0.75 V.
9. When the balancing length is obtained, the potential drop across that length of the potentiometer wire is equal to the:
A.
Resistance of the cell
B.
Current in the cell
C.
Potential difference being measured
D.
Total resistance of the wire
Correct Answer:
Potential difference being measured
Explanation:
At balance, the potential drop across the balancing length equals the potential difference of the cell under measurement.
10. On a uniform potentiometer wire, a cell balances at 50 cm. If the potential gradient is doubled without changing the cell, the new balancing length will be:
A.
25 cm
B.
50 cm
C.
100 cm
D.
200 cm
Correct Answer:
25 cm
Explanation:
For the same cell, E = k l. If the potential gradient doubles, the balancing length becomes half, so it changes from 50 cm to 25 cm.