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. The principle of a potentiometer is based on the fact that the potential drop across a uniform wire is directly proportional to its length when
A.
the current through the wire is constant
B.
the resistance of the wire is zero
C.
the length of the wire is zero
D.
the wire is connected to an open circuit
Correct Answer:
the current through the wire is constant
Explanation:
For a uniform potentiometer wire carrying constant current, resistance is proportional to length, so the potential drop is also directly proportional to length.
2. If the potential gradient of a potentiometer wire is k, the potential difference across a length l of the wire is
A.
V = k + l
B.
V = k/l
C.
V = kl
D.
V = l/k
Correct Answer:
V = kl
Explanation:
Potential gradient is the potential drop per unit length. Therefore, the potential difference across length l is V = k l.
3. The potential gradient along a uniform potentiometer wire is
A.
constant when the current is constant
B.
zero for every current
C.
always equal to the total resistance
D.
independent of the wire length and current in all cases
Correct Answer:
constant when the current is constant
Explanation:
A uniform wire has equal resistance per unit length. With constant current, the potential drop per unit length, called the potential gradient, remains constant.
4. At the balance point of a potentiometer, the potential difference being measured is equal to
A.
the potential drop across the balancing length of the wire
B.
the total resistance of the potentiometer wire
C.
the current through the galvanometer
D.
the length of the entire potentiometer wire only
Correct Answer:
the potential drop across the balancing length of the wire
Explanation:
At balance, the unknown potential difference equals the potential drop along the corresponding balancing length of the potentiometer wire.
5. For a uniform potentiometer wire, if the balancing length is doubled while the potential gradient remains unchanged, the measured potential difference becomes
A.
half
B.
unchanged
C.
double
D.
four times
Correct Answer:
double
Explanation:
Since potential difference V is directly proportional to balancing length l when the potential gradient is constant, doubling l doubles V.
6. The potential drop per unit length of a potentiometer wire is called
A.
potential gradient
B.
electric resistance
C.
charge density
D.
current density
Correct Answer:
potential gradient
Explanation:
Potential gradient is defined as the potential difference divided by the corresponding length of the potentiometer wire.
7. If the current through a uniform potentiometer wire is increased, its potential gradient generally
A.
decreases
B.
increases
C.
becomes zero
D.
remains unchanged in every case
Correct Answer:
increases
Explanation:
The potential gradient is proportional to the current for a wire of fixed resistance per unit length. Hence, increasing current increases the potential gradient.
8. A potentiometer can compare two potential differences because, for a uniform wire carrying constant current, potential difference is proportional to
A.
the balancing length
B.
the mass of the wire
C.
the diameter of the wire only
D.
the temperature of the surroundings only
Correct Answer:
the balancing length
Explanation:
The potentiometer principle states that the potential drop along a uniform wire is directly proportional to its length, so potential differences can be compared using balancing lengths.
9. If equal potential differences are balanced on the same uniform potentiometer wire under the same current condition, their balancing lengths are
A.
always unequal
B.
equal
C.
inversely proportional to the wire resistance
D.
independent of the potential differences
Correct Answer:
equal
Explanation:
With the same potential gradient, equal potential differences produce equal balancing lengths because V = k l.
10. What is the basic principle of a potentiometer?
A.
Current is directly proportional to resistance
B.
Potential drop is directly proportional to the length of a uniform wire carrying constant current
C.
Resistance is directly proportional to potential difference only
D.
Potential difference is independent of wire length
Correct Answer:
Potential drop is directly proportional to the length of a uniform wire carrying constant current
Explanation:
For a uniform potentiometer wire carrying constant current, the potential gradient is constant, so the potential drop varies directly with the length of the wire.