Q. If the distance between the slits in a double-slit experiment is halved, what happens to the angular position of the first-order maximum? (2023)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
If the slit separation d is halved, the angle θ for the first-order maximum (d sin θ = λ) will increase, effectively doubling the angle.
Correct Answer: A — It doubles
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Q. If the distance between two masses is doubled, what happens to the gravitational force between them? (2020)
A.
It doubles
B.
It halves
C.
It becomes one-fourth
D.
It becomes four times
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Solution
According to the inverse square law, if the distance is doubled, the force becomes 1/(2^2) = 1/4 of the original force.
Correct Answer: C — It becomes one-fourth
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Q. If the distance between two point charges is tripled, how does the electrostatic force between them change? (2020)
A.
It triples
B.
It halves
C.
It becomes one-ninth
D.
It remains the same
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Solution
According to Coulomb's law, the force F is inversely proportional to the square of the distance (F ∝ 1/r^2). If r is tripled, F becomes 1/9 of its original value.
Correct Answer: C — It becomes one-ninth
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Q. If the distance from the slits to the screen in a double-slit experiment is increased, what happens to the fringe pattern? (2023)
A.
Fringe width decreases
B.
Fringe width increases
C.
Fringe visibility decreases
D.
Fringe pattern disappears
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Solution
Increasing the distance from the slits to the screen increases the fringe width, as fringe width β is proportional to the distance.
Correct Answer: B — Fringe width increases
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Q. If the electric field between the plates of a capacitor is E, what is the potential difference between the plates separated by a distance d? (2020)
A.
E/d
B.
Ed
C.
d/E
D.
E*d
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Solution
The potential difference (V) between the plates is given by V = Ed, where E is the electric field and d is the distance between the plates.
Correct Answer: B — Ed
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Q. If the equilibrium constant Kc for a reaction is 10, what is the value of Kc for the reverse reaction? (2020)
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Solution
For the reverse reaction, Kc is the reciprocal of the forward reaction. Therefore, Kc (reverse) = 1/Kc (forward) = 1/10 = 0.1.
Correct Answer: A — 0.1
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Q. If the freezing point of a solution is -5°C, what is the molality of the solution if the freezing point depression constant (Kf) is 1.86°C kg/mol? (2022)
A.
1.34 m
B.
2.68 m
C.
0.5 m
D.
3.72 m
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Solution
ΔTf = Kf * m; -5 = -1.86 * m; m = 5 / 1.86 = 2.68 m.
Correct Answer: B — 2.68 m
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Q. If the freezing point of pure water is 0 °C, what will be the freezing point of a solution containing 1 mole of NaCl in 1 kg of water? (2023)
A.
-1.86 °C
B.
-3.72 °C
C.
-2.26 °C
D.
-0.93 °C
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Solution
Freezing point depression = i * Kf * m = 2 * 1.86 °C kg/mol * 1 mol/kg = 3.72 °C. Thus, freezing point = 0 - 3.72 = -3.72 °C.
Correct Answer: B — -3.72 °C
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Q. If the frequency of a simple harmonic oscillator is doubled, what happens to its period? (2021)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
The period T is inversely proportional to frequency f. If f is doubled, T is halved.
Correct Answer: B — It halves
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Q. If the frequency of an AC source is 50 Hz, what is the time period of the AC signal? (2019)
A.
0.02 s
B.
0.01 s
C.
0.5 s
D.
1 s
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Solution
The time period (T) is the reciprocal of frequency (f). Therefore, T = 1/f = 1/50 Hz = 0.02 s.
Correct Answer: A — 0.02 s
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Q. If the frequency of an AC source is increased, what happens to the inductive reactance? (2019)
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
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Solution
Inductive reactance (X_L) is directly proportional to frequency (f). Therefore, if frequency increases, X_L decreases.
Correct Answer: B — Decreases
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Q. If the inductance of a coil is doubled, what happens to its inductive reactance at a constant frequency? (2022)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Inductive reactance (X_L) is given by X_L = 2πfL. If the inductance (L) is doubled, X_L will also double.
Correct Answer: A — It doubles
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Q. If the length of a wire is doubled while keeping the diameter constant, what happens to its resistance? (2019)
A.
It doubles
B.
It halves
C.
It quadruples
D.
It remains the same
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Solution
Resistance (R) is directly proportional to length (L). If length is doubled, resistance also doubles.
Correct Answer: A — It doubles
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Q. If the magnetic flux through a coil changes from 0.5 Wb to 0.2 Wb in 2 seconds, what is the average induced emf? (2023)
A.
150 V
B.
100 V
C.
75 V
D.
50 V
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Solution
Average induced emf = -ΔΦ/Δt = -(0.2 - 0.5)/2 = 0.15 V = 150 V.
Correct Answer: B — 100 V
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Q. If the magnetic flux through a coil changes, what happens to the induced EMF? (2023)
A.
It remains constant
B.
It increases
C.
It decreases
D.
It is induced
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Solution
An induced EMF is generated when there is a change in magnetic flux through a coil.
Correct Answer: D — It is induced
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Q. If the mass of the Earth were to double while its radius remains the same, what would happen to the acceleration due to gravity? (2022)
A.
It would double
B.
It would remain the same
C.
It would halve
D.
It would increase by a factor of four
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Solution
If the mass of the Earth doubles, the acceleration due to gravity also doubles, as it is directly proportional to mass.
Correct Answer: A — It would double
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Q. If the moment of inertia of a body is doubled while keeping the angular velocity constant, what happens to its angular momentum? (2019)
A.
It doubles
B.
It remains the same
C.
It halves
D.
It quadruples
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Solution
Angular momentum L = Iω, so if I is doubled and ω remains constant, L also doubles.
Correct Answer: A — It doubles
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Q. If the potential difference across a capacitor is halved, what happens to the energy stored in the capacitor? (2019)
A.
Halved
B.
Doubled
C.
Remains the same
D.
Quadrupled
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Solution
The energy stored in a capacitor is given by U = 1/2 CV^2. If V is halved, the energy becomes U' = 1/2 C(V/2)^2 = 1/8 CV^2, which is halved.
Correct Answer: A — Halved
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Q. If the potential difference across a capacitor is increased, what happens to the charge stored in it? (2020)
A.
It decreases
B.
It remains the same
C.
It increases
D.
It becomes zero
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Solution
The charge (Q) stored in a capacitor is directly proportional to the potential difference (V) across it, given by Q = CV.
Correct Answer: C — It increases
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Q. If the potential difference between two points is 10 V and the work done to move a charge of 2 C between these points is: (2020)
A.
5 J
B.
10 J
C.
20 J
D.
40 J
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Solution
Work done (W) = Charge (Q) × Potential difference (V) = 2 C × 10 V = 20 J.
Correct Answer: C — 20 J
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Q. If the radius of a rotating object is halved while keeping the angular velocity constant, what happens to its linear velocity? (2022)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Linear velocity v = rω, so if r is halved and ω remains constant, v also halves.
Correct Answer: B — It halves
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Q. If the radius of curvature of a concave mirror is 20 cm, what is its focal length? (2022)
A.
5 cm
B.
10 cm
C.
15 cm
D.
20 cm
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Solution
The focal length (f) of a concave mirror is given by f = R/2, where R is the radius of curvature. Thus, f = 20 cm / 2 = 10 cm.
Correct Answer: B — 10 cm
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Q. If the radius of curvature of a convex lens is 20 cm, what is its focal length? (2022)
A.
10 cm
B.
20 cm
C.
30 cm
D.
40 cm
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Solution
The focal length f of a lens is given by f = R/2. Therefore, f = 20 cm / 2 = 10 cm.
Correct Answer: B — 20 cm
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Q. If the radius of curvature of a convex mirror is 20 cm, what is its focal length? (2022)
A.
10 cm
B.
20 cm
C.
30 cm
D.
40 cm
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Solution
The focal length (f) of a mirror is given by f = R/2. For a convex mirror, R is positive, so f = 20 cm / 2 = 10 cm.
Correct Answer: A — 10 cm
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Q. If the resistance of a conductor is doubled while the voltage remains constant, what happens to the current? (2020)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Ohm's Law, if the resistance (R) is doubled and the voltage (V) remains constant, the current (I) will be halved (I = V/R).
Correct Answer: B — It halves
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Q. If the vapor pressure of pure solvent is 100 mmHg, and the vapor pressure of the solution is 80 mmHg, what is the mole fraction of the solute? (2022)
A.
0.2
B.
0.4
C.
0.5
D.
0.8
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Solution
Using Raoult's Law: P_solution = X_solvent * P_solvent. X_solvent = P_solution / P_solvent = 80/100 = 0.8, thus X_solute = 1 - X_solvent = 0.2.
Correct Answer: B — 0.4
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Q. If the vapor pressure of pure solvent is 100 mmHg, and the vapor pressure of the solution is 80 mmHg, what is the relative lowering of vapor pressure? (2022)
A.
0.2
B.
0.1
C.
0.5
D.
0.3
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Solution
Relative lowering of vapor pressure = (P° - P) / P° = (100 - 80) / 100 = 0.2.
Correct Answer: A — 0.2
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Q. If the voltage across a capacitor in an AC circuit is 100 V RMS, what is the peak voltage? (2022)
A.
100 V
B.
141.42 V
C.
200 V
D.
70.71 V
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Solution
The peak voltage (V_peak) is calculated as V_peak = V_rms × √2 = 100 V × √2 ≈ 141.42 V.
Correct Answer: B — 141.42 V
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Q. If the voltage across a resistor is increased from 5V to 10V, what happens to the current through the resistor if the resistance is constant? (2021)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Ohm's law, if voltage increases and resistance remains constant, current will also increase proportionally.
Correct Answer: A — It doubles
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Q. If the voltage across an inductor is 100 V and the current through it is 2 A, what is the inductive reactance? (2023)
A.
50 Ω
B.
200 Ω
C.
100 Ω
D.
25 Ω
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Solution
Inductive reactance (X_L) is given by X_L = V/I. Here, X_L = 100 V / 2 A = 50 Ω.
Correct Answer: A — 50 Ω
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