Undergraduate
Q. In a circuit, if the resistance is halved while the voltage remains constant, what happens to the current? (2022)
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A.
It halves
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B.
It doubles
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C.
It remains the same
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D.
It quadruples
Solution
According to Ohm's law, I = V/R. If R is halved, I will double.
Correct Answer: B — It doubles
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Q. In a class of 30 students, 18 are girls. What is the probability of randomly selecting a boy? (2021)
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A.
3/5
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B.
2/5
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C.
1/2
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D.
1/3
Solution
Number of boys = 30 - 18 = 12. Probability = 12/30 = 2/5.
Correct Answer: B — 2/5
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Q. In a closed system, if 100 J of heat is added and 40 J of work is done by the system, what is the change in internal energy? (2022)
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A.
60 J
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B.
40 J
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C.
100 J
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D.
Zero
Solution
According to the First Law of Thermodynamics, ΔU = Q - W. Here, ΔU = 100 J - 40 J = 60 J.
Correct Answer: A — 60 J
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Q. In a concave lens, the focal length is: (2023)
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A.
Positive
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B.
Negative
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C.
Zero
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D.
Infinite
Solution
The focal length of a concave lens is negative, indicating that it diverges light rays.
Correct Answer: B — Negative
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Q. In a concentration cell, if the concentration of one half-cell is 0.1 M and the other is 1 M, what is the cell potential?
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A.
0.059 V
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B.
0.118 V
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C.
0.0591 V
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D.
0.1181 V
Solution
Using the Nernst equation, E = (0.0591/n) log([C1/C2]), where n=1.
Correct Answer: B — 0.118 V
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Q. In a cyclic process, the net work done is equal to: (2020)
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A.
Net heat added
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B.
Change in internal energy
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C.
Zero
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D.
Net heat removed
Solution
In a cyclic process, the net work done is equal to the net heat added to the system, as the internal energy returns to its initial state.
Correct Answer: A — Net heat added
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Q. In a damped harmonic oscillator, what happens to the amplitude over time? (2023)
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A.
Increases
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B.
Decreases
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C.
Remains constant
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D.
Oscillates
Solution
In a damped harmonic oscillator, the amplitude decreases over time due to energy loss.
Correct Answer: B — Decreases
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Q. In a Daniell cell, which metal acts as the anode?
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A.
Copper
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B.
Zinc
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C.
Silver
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D.
Lead
Solution
In a Daniell cell, Zinc acts as the anode.
Correct Answer: B — Zinc
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Q. In a dihybrid cross, what is the expected phenotypic ratio? (2023)
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A.
1:1
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B.
3:1
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C.
9:3:3:1
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D.
1:2:1
Solution
The expected phenotypic ratio in a dihybrid cross is 9:3:3:1.
Correct Answer: C — 9:3:3:1
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Q. In a double-slit experiment, if the wavelength of light is halved, what happens to the fringe width? (2020)
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A.
It doubles
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B.
It halves
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C.
It remains the same
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D.
It quadruples
Solution
Fringe width (β) is given by β = λD/d. If λ is halved, β will also be halved.
Correct Answer: A — It doubles
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Q. In a first-order reaction, if the concentration of reactant decreases from 0.8 M to 0.2 M in 20 minutes, what is the rate constant? (2022)
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A.
0.0347 min⁻¹
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B.
0.0693 min⁻¹
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C.
0.1 min⁻¹
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D.
0.2 min⁻¹
Solution
Using the first-order rate equation, k = (ln[A₀] - ln[A]) / t. Here, k = (ln(0.8) - ln(0.2)) / 20 = 0.0347 min⁻¹.
Correct Answer: A — 0.0347 min⁻¹
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Q. In a first-order reaction, if the rate constant k is 0.03 min⁻¹, what is the time required for the concentration to decrease to half? (2020)
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A.
23.1 min
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B.
10.0 min
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C.
20.0 min
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D.
15.0 min
Solution
t₁/₂ = 0.693 / k = 0.693 / 0.03 = 23.1 min.
Correct Answer: A — 23.1 min
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Q. In a food chain, which of the following is a primary consumer? (2019)
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A.
Grass
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B.
Rabbit
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C.
Fox
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D.
Eagle
Solution
A rabbit is a primary consumer as it feeds on plants (producers).
Correct Answer: B — Rabbit
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Q. In a galvanic cell, if the anode reaction is 2Ag⁺ + 2e⁻ → 2Ag, what is the cathode reaction? (2022)
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A.
Cu²⁺ + 2e⁻ → Cu
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B.
Zn²⁺ + 2e⁻ → Zn
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C.
Fe²⁺ + 2e⁻ → Fe
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D.
Pb²⁺ + 2e⁻ → Pb
Solution
The cathode reaction must be a reduction reaction, and Cu²⁺ + 2e⁻ → Cu is a common cathode reaction.
Correct Answer: A — Cu²⁺ + 2e⁻ → Cu
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Q. In a galvanic cell, if the anode reaction is 2H₂ → 4H⁺ + 4e⁻, what is the cathode reaction?
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A.
O₂ + 4e⁻ + 4H⁺ → 2H₂O
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B.
2H₂O + 4e⁻ → 2H₂ + O₂
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C.
4H⁺ + 4e⁻ → 2H₂
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D.
2H₂ + O₂ → 2H₂O
Solution
The cathode reaction is O₂ + 4e⁻ + 4H⁺ → 2H₂O.
Correct Answer: A — O₂ + 4e⁻ + 4H⁺ → 2H₂O
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Q. In a galvanic cell, if the anode reaction is Ag⁺ + e⁻ → Ag, what is the cathode reaction?
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A.
Cu²⁺ + 2e⁻ → Cu
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B.
Zn²⁺ + 2e⁻ → Zn
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C.
Fe²⁺ + 2e⁻ → Fe
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D.
Pb²⁺ + 2e⁻ → Pb
Solution
The cathode reaction must be a reduction; Ag⁺ + e⁻ → Ag is the anode reaction.
Correct Answer: A — Cu²⁺ + 2e⁻ → Cu
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Q. In a galvanic cell, if the anode reaction is Zn → Zn²⁺ + 2e⁻, what is the cathode reaction if the cathode is Cu²⁺ + 2e⁻ → Cu?
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A.
Cu → Cu²⁺ + 2e⁻
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B.
Zn²⁺ + 2e⁻ → Zn
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C.
Zn + Cu²⁺ → Zn²⁺ + Cu
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D.
Cu²⁺ + 2e⁻ → Cu
Solution
The cathode reaction is Cu²⁺ + 2e⁻ → Cu.
Correct Answer: D — Cu²⁺ + 2e⁻ → Cu
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Q. In a group of 50 people, 20 are smokers. What is the probability of selecting a non-smoker? (2022)
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A.
2/5
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B.
3/5
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C.
1/2
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D.
1/4
Solution
Number of non-smokers = 50 - 20 = 30. Probability = 30/50 = 3/5.
Correct Answer: B — 3/5
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Q. In a harmonic oscillator, if the mass is doubled while keeping the spring constant the same, how does the frequency change? (2021)
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A.
Increases
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B.
Decreases
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C.
Remains the same
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D.
Becomes zero
Solution
Frequency (f) = (1/2π)√(k/m). If mass (m) is doubled, frequency decreases.
Correct Answer: B — Decreases
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Q. In a heat engine, if the input heat is 500 J and the work done is 300 J, what is the efficiency? (2023) 2023
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A.
60%
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B.
50%
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C.
40%
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D.
70%
Solution
Efficiency (η) = Work done / Input heat = 300 J / 500 J = 0.6 or 60%.
Correct Answer: A — 60%
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Q. In a lottery, there are 10 tickets, and 2 are winning tickets. What is the probability of picking a winning ticket?
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A.
1/5
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B.
1/10
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C.
1/2
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D.
2/10
Solution
Probability = Number of winning tickets / Total tickets = 2/10 = 1/5.
Correct Answer: A — 1/5
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Q. In a lottery, there are 10 tickets, and 3 are winning tickets. What is the probability of picking a winning ticket? (2022)
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A.
1/3
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B.
1/4
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C.
1/5
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D.
1/2
Solution
Probability = Number of winning tickets / Total tickets = 3/10.
Correct Answer: A — 1/3
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Q. In a parallel circuit with two resistors of 6Ω and 3Ω, what is the total resistance? (2019)
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A.
2Ω
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B.
4Ω
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C.
1.5Ω
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D.
9Ω
Solution
Using the formula 1/R_eq = 1/R1 + 1/R2, we get 1/R_eq = 1/6 + 1/3 = 1/6 + 2/6 = 3/6, thus R_eq = 2Ω.
Correct Answer: B — 4Ω
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Q. In a parallel RLC circuit, if R = 50 ohms, L = 0.2H, and C = 50μF, what is the total admittance? (2023)
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A.
0.02 S
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B.
0.04 S
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C.
0.06 S
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D.
0.08 S
Solution
Y = 1/R + j(ωC - 1/ωL); calculate Y for given values.
Correct Answer: C — 0.06 S
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Q. In a parallel RLC circuit, if R = 50Ω, L = 0.2 H, and C = 50μF, what is the quality factor Q? (2015)
Solution
Quality factor Q = (1/R) * √(L/C) = (1/50) * √(0.2/50e-6) = 2.
Correct Answer: B — 2
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Q. In a PN junction diode, what happens when it is forward biased? (2019)
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A.
Depletion region widens
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B.
Depletion region narrows
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C.
No current flows
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D.
Reverse current increases
Solution
When a PN junction diode is forward biased, the depletion region narrows, allowing current to flow.
Correct Answer: B — Depletion region narrows
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Q. In a predator-prey relationship, which of the following is true? (2022)
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A.
Predators are always larger than their prey.
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B.
Prey populations are always larger than predator populations.
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C.
Predators help control prey populations.
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D.
Prey can never escape predators.
Solution
Predators help control the population of prey species, maintaining a balance in the ecosystem.
Correct Answer: C — Predators help control prey populations.
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Q. In a purely capacitive AC circuit, the current leads the voltage by how many degrees? (2022)
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A.
0°
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B.
90°
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C.
180°
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D.
270°
Solution
In a purely capacitive circuit, the current leads the voltage by 90°.
Correct Answer: B — 90°
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Q. In a purely capacitive AC circuit, the current leads the voltage by how much phase angle? (2023)
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A.
0 degrees
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B.
90 degrees
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C.
180 degrees
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D.
270 degrees
Solution
In a purely capacitive circuit, the current leads the voltage by 90 degrees.
Correct Answer: B — 90 degrees
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Q. In a reaction A → B, if the concentration of A decreases from 0.8 M to 0.4 M in 20 minutes, what is the average rate of reaction? (2019)
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A.
0.02 M/min
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B.
0.04 M/min
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C.
0.1 M/min
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D.
0.05 M/min
Solution
Average rate = Δ[A]/Δt = (0.8 - 0.4) / 20 = 0.02 M/min.
Correct Answer: D — 0.05 M/min
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