physics : class12 Advantages of Potentiometer : Potentiometer : Current Electricity MCQ Questions and Answers
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Advantages of Potentiometer
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MCQ Questions
1. What is a major advantage of a potentiometer over a voltmeter for measuring the emf of a cell?
A.
It draws no current from the cell at the balance point
B.
It always increases the emf of the cell
C.
It has no resistance in its circuit
D.
It works without a battery
Correct Answer:
It draws no current from the cell at the balance point
Explanation:
At the balance point, a potentiometer uses a null method, so no current is drawn from the cell being measured. This makes the emf measurement more accurate.
2. Why is a potentiometer generally more accurate than a voltmeter for comparing the emfs of two cells?
A.
It measures current directly
B.
It uses a null method
C.
It has a smaller scale
D.
It always uses a stronger cell
Correct Answer:
It uses a null method
Explanation:
A potentiometer compares emfs at balance without drawing current from the cells. Therefore, the result is not affected by the internal resistance of the cells during measurement.
3. Which quantity can be measured accurately using a potentiometer because of its null method?
A.
The emf of a cell
B.
The mass of a cell
C.
The temperature of a wire only
D.
The length of the connecting wires only
Correct Answer:
The emf of a cell
Explanation:
The null method of a potentiometer allows the emf of a cell to be measured accurately without drawing current from the cell at balance.
4. A potentiometer can be used to determine the internal resistance of a cell. What makes this possible?
A.
It can compare the emf and terminal potential difference of the cell
B.
It removes the internal resistance of the cell
C.
It converts electrical energy into heat
D.
It measures the mass of the electrolyte
Correct Answer:
It can compare the emf and terminal potential difference of the cell
Explanation:
By measuring the emf and the terminal potential difference under load, a potentiometer can be used to calculate the internal resistance of the cell.
5. Which feature of a potentiometer makes it suitable for detecting small potential differences?
A.
A long and uniform resistance wire
B.
A very short connecting wire
C.
A large metal plate
D.
A thick insulating cover
Correct Answer:
A long and uniform resistance wire
Explanation:
A long uniform wire provides a small and uniform potential gradient. Hence, even a small potential difference can produce a measurable shift in the balance point.
6. What is the main advantage of using a potentiometer instead of a voltmeter to compare two cell emfs?
A.
The comparison is independent of the cells' internal resistances at balance
B.
The potentiometer increases both cell currents
C.
The voltmeter becomes part of the primary circuit
D.
The cells need not be connected to any circuit
Correct Answer:
The comparison is independent of the cells' internal resistances at balance
Explanation:
Since no current is drawn from the cells at the balance point, their internal resistances do not affect the emf comparison.
7. Why is a potentiometer called a more sensitive instrument than an ordinary voltmeter for small voltage measurements?
A.
It can detect a small voltage by locating a balance point
B.
It always has zero resistance
C.
It produces voltage without a source
D.
It measures voltage only at high current
Correct Answer:
It can detect a small voltage by locating a balance point
Explanation:
The balance-point method allows a potentiometer to detect very small potential differences accurately, making it more sensitive than an ordinary voltmeter for such measurements.
8. Which advantage of a potentiometer is useful when calibrating a voltmeter?
A.
It provides a more accurate standard potential difference
B.
It eliminates the need for any electrical source
C.
It changes alternating current into direct current
D.
It measures resistance without a circuit
Correct Answer:
It provides a more accurate standard potential difference
Explanation:
A potentiometer can produce a known potential difference using its potential gradient and balance length. This accurate value can be used to calibrate a voltmeter.
9. At the balance point of a potentiometer, what is an important advantage regarding the galvanometer?
A.
It shows zero deflection, indicating no current through the test circuit
B.
It gives the maximum possible deflection
C.
It measures the resistance of the potentiometer wire directly
D.
It supplies power to the cell under test
Correct Answer:
It shows zero deflection, indicating no current through the test circuit
Explanation:
Zero galvanometer deflection marks the null condition. No current flows through the branch containing the cell under test, which improves the accuracy of measurement.
10. Which statement best describes an advantage of increasing the length of the potentiometer wire?
A.
It decreases the potential gradient and improves sensitivity
B.
It removes the need for a battery
C.
It makes the wire completely resistance-free
D.
It prevents the use of a galvanometer
Correct Answer:
It decreases the potential gradient and improves sensitivity
Explanation:
For a given potential difference, a longer wire has a smaller potential drop per unit length. This allows small potential differences to be measured more precisely.
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