Q. A potentiometer is used to compare two emf sources. If the first source gives a balance length of 60cm and the second gives 90cm, what is the ratio of their emfs?
A.2:3
B.3:2
C.1:1
D.4:5
Solution
The ratio of emfs is equal to the ratio of the balance lengths, so it is 60cm:90cm = 2:3.
Q. A potentiometer is used to compare two EMFs. If the known EMF is 6V and the length of the wire is 120 cm, what is the potential gradient if the length of the wire is used to balance an unknown EMF of 4V?
A.0.05 V/cm
B.0.03 V/cm
C.0.04 V/cm
D.0.02 V/cm
Solution
The potential gradient is calculated as (6V / 120 cm) = 0.05 V/cm. For the unknown EMF of 4V, the length used would be (4V / 0.05 V/cm) = 80 cm.
Q. A potentiometer wire has a uniform cross-section and a potential difference of 12V across it. If the length of the wire is 6m, what is the potential gradient?
Q. A potentiometer wire has a uniform cross-section and a total length of 10 m. If a potential difference of 5 V is applied across it, what is the potential gradient?
A.0.5 V/m
B.1 V/m
C.2 V/m
D.5 V/m
Solution
The potential gradient is calculated as V/L = 5 V / 10 m = 0.5 V/m.
Q. If a potentiometer is used to compare two cells, what is the effect of increasing the length of the wire?
A.It increases the accuracy of the measurement
B.It decreases the accuracy of the measurement
C.It has no effect on the measurement
D.It makes the cells equal
Solution
Increasing the length of the wire increases the potential gradient, which can improve the accuracy of the measurement by allowing for finer adjustments.
Correct Answer: A — It increases the accuracy of the measurement
Q. If a potentiometer is used to compare two emfs, what is the key requirement for the two circuits?
A.They must have the same resistance
B.They must have the same length of wire
C.They must be connected in series
D.They must have the same potential gradient
Solution
For accurate comparison of two emfs using a potentiometer, both circuits must have the same potential gradient to ensure that the readings are directly comparable.
Correct Answer: D — They must have the same potential gradient
Q. If a potentiometer is used to measure the EMF of a cell and the balance point is found at 3 m, what can be inferred about the cell's EMF if the potential gradient is 1.5 V/m?
A.1.5 V
B.3 V
C.4.5 V
D.6 V
Solution
The EMF of the cell can be calculated as EMF = potential gradient × length = 1.5 V/m × 3 m = 4.5 V.
Q. If the balancing length of a potentiometer is found to be 40 cm for a cell of emf 2V, what is the potential gradient if the total length of the wire is 100 cm?
Q. If the emf of a cell is 12 V and the potentiometer wire is 20 m long, what is the potential gradient if the wire is calibrated to give a reading of 0.6 V/m?
A.12 V
B.0.6 V/m
C.0.3 V/m
D.0.5 V/m
Solution
The potential gradient is given as 0.6 V/m, which is the calibration value for the potentiometer.
Q. If the internal resistance of a cell is negligible, how does it affect the accuracy of a potentiometer measurement?
A.It increases accuracy
B.It decreases accuracy
C.It has no effect
D.It makes the measurement impossible
Solution
If the internal resistance of a cell is negligible, it increases the accuracy of the potentiometer measurement as it does not affect the voltage being measured.
Q. If the length of the potentiometer wire is increased while keeping the voltage constant, what will happen to the balance point when measuring a cell's EMF?
A.It will move to a longer length.
B.It will move to a shorter length.
C.It will remain unchanged.
D.It will become unstable.
Solution
Increasing the length of the potentiometer wire while keeping the voltage constant will increase the balance point length for the same EMF.
Correct Answer: A — It will move to a longer length.
Q. If the resistance of the potentiometer wire is increased, what effect does it have on the measurement accuracy?
A.Increases accuracy
B.Decreases accuracy
C.No effect
D.Depends on the length of the wire
Solution
Increasing the resistance of the potentiometer wire can lead to a larger voltage drop, which may decrease measurement accuracy due to increased error in balancing.
Q. In a potentiometer circuit, if the balancing length is 50 cm for a cell of emf 1.5V, what is the potential gradient if the total length of the wire is 100 cm?
A.3 V/m
B.1.5 V/m
C.0.75 V/m
D.2 V/m
Solution
The potential gradient is V/L = 1.5V/0.5m = 3 V/m, but since the total length is 1m, the gradient is 1.5 V/m.
Q. In a potentiometer circuit, if the length of the wire is doubled while keeping the potential difference constant, what happens to the potential gradient?
A.It doubles
B.It halves
C.It remains the same
D.It becomes zero
Solution
The potential gradient is defined as the potential difference per unit length. If the length is doubled while keeping the potential difference constant, the potential gradient halves.
Q. In a potentiometer circuit, if the length of the wire is doubled, what happens to the potential gradient?
A.It doubles.
B.It halves.
C.It remains the same.
D.It quadruples.
Solution
The potential gradient is defined as the potential difference per unit length. If the length is doubled with the same potential difference, the gradient halves.
