Q. In a photoelectric experiment, if the frequency of light is just above the threshold frequency, what can be said about the emitted electrons?
A.They have maximum kinetic energy
B.They are emitted with zero kinetic energy
C.They are emitted with high kinetic energy
D.No electrons are emitted
Solution
If the frequency of light is just above the threshold frequency, the emitted electrons will have zero kinetic energy, as all the energy is used to overcome the work function.
Correct Answer: B — They are emitted with zero kinetic energy
Q. In a photoelectric experiment, if the stopping potential is increased, what happens to the maximum kinetic energy of the emitted electrons?
A.It increases
B.It decreases
C.It remains the same
D.It becomes zero
Solution
Increasing the stopping potential increases the maximum kinetic energy of the emitted electrons, as the stopping potential is directly related to the kinetic energy of the electrons.
Q. In a physics experiment, the force applied is measured as 50 N with an uncertainty of ±1 N. What is the relative uncertainty in the force measurement?
Q. In a physics experiment, the speed of an object is measured as 20.0 m/s with an uncertainty of ±0.4 m/s. What is the maximum possible error in the kinetic energy calculated from this speed?
A.8 J
B.4 J
C.2 J
D.1 J
Solution
Kinetic energy = 0.5 * m * v²; maximum error = m * v * uncertainty in v = m * 20.0 * 0.4 = 8 J (assuming m = 1 kg).
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.
Q. In a potentiometer experiment, if the balance point is found at 4 m with a 6 V battery, what is the voltage across a cell connected to the potentiometer?
A.2 V
B.3 V
C.4 V
D.6 V
Solution
Using the potential gradient, we can find the voltage across the cell. The potential gradient is 6 V / 10 m = 0.6 V/m. At 4 m, the voltage is 0.6 V/m * 4 m = 2.4 V, which rounds to 2 V.
Q. In a potentiometer experiment, if the balance point is found at 4 m with a known voltage of 12 V, what is the unknown voltage if the balance point for it is at 6 m?
A.8 V
B.9 V
C.18 V
D.24 V
Solution
Using the formula V1/L1 = V2/L2, we have 12 V / 4 m = V2 / 6 m. Solving gives V2 = 18 V.
Q. In a potentiometer experiment, if the balance point shifts when a load is connected, what does it indicate?
A.The load has infinite resistance
B.The load has zero resistance
C.The load affects the circuit's total resistance
D.The potentiometer is faulty
Solution
A shift in the balance point indicates that the load connected affects the total resistance in the circuit, altering the potential difference across the potentiometer wire.
Correct Answer: C — The load affects the circuit's total resistance
Q. In a potentiometer experiment, if the balancing length is found to be 4m for a cell of unknown EMF, what is the EMF if the potential gradient is 3 V/m?
A.6 V
B.8 V
C.12 V
D.15 V
Solution
EMF = Potential Gradient × Balancing Length = 3 V/m × 4 m = 12 V.
Q. In a potentiometer experiment, if the balancing length is found to be 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.0.5 V/m
D.2 V/m
Solution
The potential gradient is V/L = 1.5V/0.5m = 3 V/m.
Q. In a potentiometer experiment, if the known voltage is increased, what effect does it have on the balance point?
A.Balance point moves towards the positive terminal
B.Balance point moves towards the negative terminal
C.Balance point remains unchanged
D.Balance point becomes unstable
Solution
Increasing the known voltage will cause the balance point to move towards the positive terminal, as a higher voltage requires a longer length of wire to achieve balance.
Correct Answer: A — Balance point moves towards the positive terminal
Q. In a potentiometer experiment, if the known voltage is increased, what happens to the balance point?
A.It moves towards the positive terminal.
B.It moves towards the negative terminal.
C.It remains unchanged.
D.It becomes unstable.
Solution
Increasing the known voltage will cause the balance point to move towards the positive terminal, as a higher voltage requires a longer length of wire to balance.
Correct Answer: A — It moves towards the positive terminal.
Q. In a potentiometer experiment, if the null point is found at 75cm with a known emf of 1.5V, what is the potential gradient if the total length of the wire is 150cm?
A.1 V/m
B.2 V/m
C.3 V/m
D.4 V/m
Solution
The potential gradient is V/L = 1.5V/0.75m = 2 V/m.
