physics : class12 Standardization of Potentiometer : Potentiometer : Current Electricity MCQ Questions and Answers
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Standardization of Potentiometer
MCQ questions and answers.
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MCQ Questions
1. What is the main purpose of standardizing a potentiometer?
A.
To determine the potential gradient along its wire
B.
To measure the resistance of the galvanometer
C.
To increase the current through the standard cell
D.
To determine the length of the connecting wires
Correct Answer:
To determine the potential gradient along its wire
Explanation:
Standardization determines the potential drop per unit length, called the potential gradient, of the potentiometer wire.
2. Which source is used to standardize a potentiometer?
A.
A cell of unknown emf
B.
A cell of known emf
C.
A variable resistor
D.
A galvanometer
Correct Answer:
A cell of known emf
Explanation:
A standard cell having a known emf is used to find the potential gradient during standardization.
3. If a standard cell of emf E balances at length l of the potentiometer wire, the potential gradient is
A.
El
B.
E/l
C.
l/E
D.
E + l
Correct Answer:
E/l
Explanation:
The potential gradient is the potential drop per unit length, so k = E/l.
4. During standardization, the standard cell is connected to the potentiometer so that its emf is balanced against the
A.
Entire external circuit resistance
B.
Potential drop across a known length of wire
C.
Resistance of the galvanometer only
D.
Current through the standard cell
Correct Answer:
Potential drop across a known length of wire
Explanation:
The known emf of the standard cell is balanced against the potential difference across a measured length of the potentiometer wire.
5. A standard cell of emf 1.5 V balances at 300 cm. What potential difference corresponds to 100 cm of the potentiometer wire?
A.
0.05 V
B.
0.5 V
C.
1.5 V
D.
4.5 V
Correct Answer:
0.5 V
Explanation:
The potential gradient is 1.5/300 = 0.005 V/cm. For 100 cm, the potential difference is 0.005 × 100 = 0.5 V.
6. Why is a standard cell preferred for standardizing a potentiometer?
A.
Its emf is accurately known and stable
B.
It has zero internal resistance
C.
It produces unlimited current
D.
It does not require a galvanometer
Correct Answer:
Its emf is accurately known and stable
Explanation:
A standard cell provides a known and nearly constant emf, making it suitable for determining the potential gradient accurately.
7. If the balance length for a standard cell increases while its emf remains unchanged, the potential gradient becomes
A.
Larger
B.
Smaller
C.
Zero immediately
D.
Unchanged in every case
Correct Answer:
Smaller
Explanation:
Since k = E/l, an increase in balance length l with constant E decreases the potential gradient.
8. A standard cell of emf 2 V balances at 400 cm. What is the potential gradient in V/m?
A.
0.005 V/m
B.
0.05 V/m
C.
0.5 V/m
D.
5 V/m
Correct Answer:
0.5 V/m
Explanation:
The balance length is 4 m, so k = 2/4 = 0.5 V/m.
9. After standardization, the potential gradient is used to determine the emf of an unknown cell from its
A.
Balance length
B.
Wire diameter
C.
Galvanometer resistance
D.
Length of the standard cell
Correct Answer:
Balance length
Explanation:
Once k is known, the unknown emf is calculated using E = k l, where l is the balance length for the unknown cell.
10. Why is a standard cell used while standardizing a potentiometer?
A.
To provide a known emf
B.
To increase the resistance of the wire
C.
To reduce the length of the potentiometer wire
D.
To measure the current in the circuit
Correct Answer:
To provide a known emf
Explanation:
A standard cell has a known and constant emf, which is used to determine the potential gradient of the potentiometer wire during standardization.