physics : class12 Balance Point : Potentiometer : Current Electricity MCQ Questions and Answers
Practice important
Balance Point
MCQ questions and answers.
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MCQ Questions
1. In a potentiometer, the balance point is the position on the wire where the galvanometer shows:
A.
Maximum deflection
B.
Zero deflection
C.
A constant deflection
D.
Reversed deflection
Correct Answer:
Zero deflection
Explanation:
At the balance point, no current flows through the galvanometer because the potential difference across it is zero.
2. At the balance point of a potentiometer, the potential difference across the test cell is equal to:
A.
The potential drop across the balancing length
B.
Zero in every case
C.
The total potential drop across the whole wire only
D.
Twice the potential drop across the balancing length
Correct Answer:
The potential drop across the balancing length
Explanation:
The balance point is reached when the emf or potential difference of the test cell equals the potential drop along the balancing length of the potentiometer wire.
3. If the balance point is obtained at a length of 40 cm on a uniform potentiometer wire, the potential drop across the cell is proportional to:
A.
20 cm
B.
40 cm
C.
80 cm
D.
1 cm
Correct Answer:
40 cm
Explanation:
At balance, the cell potential difference is proportional to the balancing length. Therefore, it is proportional to 40 cm.
4. A potentiometer gives a balance point at 60 cm. What happens to the galvanometer deflection when the jockey is placed exactly at this point?
A.
It becomes zero
B.
It becomes maximum
C.
It changes continuously
D.
It becomes twice its original value
Correct Answer:
It becomes zero
Explanation:
At the balance point, the potential difference between the jockey point and the cell terminal is zero, so the galvanometer shows no deflection.
5. For a uniform potentiometer wire, if the potential gradient is k and the balance point is at length l, the potential difference of the cell is:
A.
k + l
B.
k - l
C.
kl
D.
k divided by l
Correct Answer:
kl
Explanation:
The potential drop across a length l is the potential gradient multiplied by that length. Hence, the cell potential difference at balance is kl.
6. A cell is balanced at 50 cm on a potentiometer wire. If the potential gradient remains unchanged, at which length would a cell having twice the potential difference be balanced?
A.
25 cm
B.
50 cm
C.
75 cm
D.
100 cm
Correct Answer:
100 cm
Explanation:
For the same potential gradient, the balance length is directly proportional to the cell potential difference. Doubling the potential difference doubles the balance length.
7. When the jockey is moved through the balance point of a potentiometer, the galvanometer deflection:
A.
Remains zero everywhere
B.
Changes its direction
C.
Always increases in the same direction
D.
Becomes independent of the cell
Correct Answer:
Changes its direction
Explanation:
On either side of the balance point, the potential difference reverses direction. Therefore, the galvanometer deflection changes its direction as the jockey crosses the balance point.
8. The balance point of a potentiometer is also called the:
A.
Null point
B.
Heating point
C.
Resistance point
D.
Maximum current point
Correct Answer:
Null point
Explanation:
It is called the null point because the galvanometer shows zero deflection at this position.
9. A cell is balanced at 80 cm on a potentiometer wire. If the potential gradient is 0.02 V/cm, the cell potential difference is:
A.
0.016 V
B.
0.16 V
C.
1.6 V
D.
40 V
Correct Answer:
1.6 V
Explanation:
At balance, the cell potential difference equals the potential drop along the balance length: E = k l = 0.02 V/cm × 80 cm = 1.6 V.
10. In a potentiometer experiment, the balance point is the position where the potential difference between the jockey point and the cell terminal is:
A.
Maximum
B.
Equal to the supply voltage
C.
Zero
D.
Equal to the resistance of the wire
Correct Answer:
Zero
Explanation:
At the balance point, the potential at the jockey point equals the potential of the corresponding cell terminal, so their potential difference is zero.