Q. In a parallel plate capacitor, if the distance between the plates is doubled while keeping the charge constant, what happens to the electric potential?
A.It doubles
B.It halves
C.It remains the same
D.It quadruples
Solution
The electric potential V is directly proportional to the distance d between the plates, so if d is doubled, V also doubles.
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.