Undergraduate
Q. In a purely capacitive AC circuit, the current leads the voltage by how many degrees? (2022)
A.
0°
B.
90°
C.
180°
D.
270°
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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)
A.
0 degrees
B.
90 degrees
C.
180 degrees
D.
270 degrees
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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)
A.
0.02 M/min
B.
0.04 M/min
C.
0.1 M/min
D.
0.05 M/min
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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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Q. In a reaction at equilibrium, if the concentration of a reactant is increased, what will happen to the equilibrium position? (2019)
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Depends on temperature
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Solution
Increasing the concentration of a reactant will shift the equilibrium position to the right, favoring the formation of products.
Correct Answer: A — Shift to the right
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Q. In a reaction at equilibrium, if the temperature is increased for an exothermic reaction, what will happen? (2022)
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase in pressure
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Solution
For an exothermic reaction, increasing the temperature shifts the equilibrium to the left, favoring the reactants.
Correct Answer: B — Shift to the left
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Q. In a reaction, if the concentration of reactant A is halved, and the rate constant remains the same, how does the rate change for a first-order reaction? (2021)
A.
Doubles
B.
Halves
C.
Remains the same
D.
Quadruples
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Solution
For a first-order reaction, if [A] is halved, the rate also halves.
Correct Answer: B — Halves
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Q. In a reaction, if the concentration of reactant A is halved, and the rate of reaction decreases to one-fourth, what is the order of the reaction? (2020)
A.
Zero
B.
First
C.
Second
D.
Third
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Solution
If the rate decreases to one-fourth when concentration is halved, the reaction is second-order.
Correct Answer: C — Second
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Q. In a redox reaction, which of the following statements is true? (2020)
A.
Oxidation involves gain of electrons
B.
Reduction involves loss of electrons
C.
Oxidation state of an element decreases during oxidation
D.
Reduction involves gain of electrons
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Solution
Reduction is defined as the gain of electrons, which decreases the oxidation state of the element.
Correct Answer: D — Reduction involves gain of electrons
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Q. In a reversible reaction, if the concentration of products increases, what happens to the equilibrium position? (2021) 2021
A.
It shifts to the left
B.
It shifts to the right
C.
It remains unchanged
D.
It shifts to the center
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Solution
According to Le Chatelier's principle, if the concentration of products increases, the equilibrium will shift to the left to counteract the change.
Correct Answer: A — It shifts to the left
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Q. In a reversible reaction, if the concentration of products increases, what happens to the equilibrium position? (2021)
A.
It shifts to the left
B.
It shifts to the right
C.
It remains unchanged
D.
It shifts to the center
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Solution
According to Le Chatelier's principle, if the concentration of products increases, the equilibrium will shift to the left to counteract the change.
Correct Answer: A — It shifts to the left
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Q. In a reversible reaction, if the concentration of products increases, what happens to the rate of the forward reaction? (2021)
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
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Solution
According to Le Chatelier's principle, if the concentration of products increases, the system will shift to the left, decreasing the rate of the forward reaction.
Correct Answer: B — It decreases
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Q. In a reversible reaction, if the concentration of reactants is increased, what will happen to the equilibrium position? (2021)
A.
It will shift to the right
B.
It will shift to the left
C.
It will remain unchanged
D.
It will shift to the center
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Solution
According to Le Chatelier's principle, if the concentration of reactants is increased, the equilibrium will shift to the right to favor the formation of products.
Correct Answer: A — It will shift to the right
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Q. In a reversible reaction, if the concentration of reactants is increased, what will happen to the position of equilibrium? (2021)
A.
It will shift to the right
B.
It will shift to the left
C.
It will remain unchanged
D.
It will shift to the center
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Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium position to the right to favor the formation of products.
Correct Answer: A — It will shift to the right
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Q. In a reversible reaction, if the forward reaction is exothermic, what can be said about the reverse reaction? (2022)
A.
It is also exothermic
B.
It is endothermic
C.
It has no effect on equilibrium
D.
It is spontaneous
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Solution
If the forward reaction is exothermic, the reverse reaction must be endothermic, as it absorbs heat.
Correct Answer: B — It is endothermic
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Q. In a second-order reaction, if the initial concentration is 0.1 M and the rate constant is 0.05 M⁻¹s⁻¹, what is the time taken to reach half the initial concentration? (2020)
A.
10 s
B.
20 s
C.
5 s
D.
15 s
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Solution
For a second-order reaction, t₁/₂ = 1 / (k[A₀]) = 1 / (0.05 * 0.1) = 200 s.
Correct Answer: B — 20 s
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Q. In a series circuit with a 9V battery and three resistors of 1Ω, 2Ω, and 3Ω, what is the total resistance? (2019)
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Solution
Total resistance in series is R_total = R1 + R2 + R3 = 1 + 2 + 3 = 6Ω.
Correct Answer: A — 6Ω
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Q. In a series circuit, if one resistor is removed, what happens to the current? (2023)
A.
It increases
B.
It decreases
C.
It remains the same
D.
It becomes zero
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Solution
In a series circuit, removing one resistor breaks the circuit, causing the current to become zero.
Correct Answer: D — It becomes zero
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Q. In a series circuit, if the resistance is doubled, what happens to the current flowing through the circuit? (2021)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It becomes zero
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Solution
According to Ohm's law, I = V/R. If R is doubled, the current I will be halved for a constant voltage V.
Correct Answer: B — It halves
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Q. In a series RLC circuit, at resonance, the impedance is equal to which of the following? (2020)
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Solution
At resonance in a series RLC circuit, the impedance (Z) is equal to the resistance (R) because the inductive and capacitive reactances cancel each other out.
Correct Answer: B — R
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Q. In a series RLC circuit, if R = 10 ohms, L = 0.1H, and C = 100μF, what is the resonant frequency? (2021)
A.
159.15 Hz
B.
100 Hz
C.
50 Hz
D.
200 Hz
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Solution
f0 = 1 / (2π√(LC)) = 1 / (2π√(0.1 × 100 × 10^-6)) = 159.15 Hz.
Correct Answer: A — 159.15 Hz
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Q. In a series RLC circuit, if R = 20Ω, L = 0.1 H, and C = 100μF, what is the resonant frequency? (2020)
A.
50 Hz
B.
100 Hz
C.
159.15 Hz
D.
200 Hz
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Solution
Resonant frequency f₀ = 1 / (2π√(LC)) = 1 / (2π√(0.1 * 100e-6)) = 159.15 Hz.
Correct Answer: C — 159.15 Hz
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Q. In a series RLC circuit, if the inductive reactance is greater than the capacitive reactance, the circuit is said to be: (2019)
A.
Resonant
B.
Capacitive
C.
Inductive
D.
Purely resistive
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Solution
If inductive reactance (XL) is greater than capacitive reactance (XC), the circuit is inductive.
Correct Answer: C — Inductive
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Q. In a series RLC circuit, if the resistance is 10 ohms, inductance is 0.1 H, and capacitance is 100 μF, what is the resonant frequency? (2021)
A.
50 Hz
B.
100 Hz
C.
159 Hz
D.
200 Hz
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Solution
Resonant frequency f = 1/(2π√(LC)) = 1/(2π√(0.1 * 100e-6)) = 159.15 Hz.
Correct Answer: C — 159 Hz
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Q. In a series RLC circuit, if the resistance is 10Ω, inductance is 0.1H, and capacitance is 100μF, what is the resonant frequency? (2021)
A.
50Hz
B.
100Hz
C.
159Hz
D.
200Hz
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Solution
Resonant frequency f0 = 1/(2π√(LC)) = 1/(2π√(0.1*100e-6)) ≈ 159Hz.
Correct Answer: C — 159Hz
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Q. In a series RLC circuit, if the resistance is 4 ohms, inductance is 0.1 H, and capacitance is 100 μF, what is the resonant frequency? (2023)
A.
50 Hz
B.
100 Hz
C.
159.15 Hz
D.
200 Hz
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Solution
Resonant frequency f = 1/(2π√(LC)) = 1/(2π√(0.1 * 100e-6)) = 159.15 Hz.
Correct Answer: C — 159.15 Hz
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Q. In a series RLC circuit, what condition must be met for resonance to occur? (2021)
A.
R = 0
B.
XL = XC
C.
R = XL
D.
R = XC
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Solution
For resonance in a series RLC circuit, the condition XL = XC must be met.
Correct Answer: B — XL = XC
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Q. In a series RLC circuit, what happens at resonance? (2020)
A.
Impedance is minimum
B.
Current is minimum
C.
Voltage is maximum
D.
Power factor is zero
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Solution
At resonance in a series RLC circuit, the impedance is minimum, and the circuit behaves like a purely resistive circuit.
Correct Answer: A — Impedance is minimum
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Q. In a series RLC circuit, what happens to the current when the circuit is at resonance? (2021)
A.
It is maximum
B.
It is minimum
C.
It is zero
D.
It is constant
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Solution
At resonance in a series RLC circuit, the impedance is minimum, and thus the current is maximum.
Correct Answer: A — It is maximum
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Q. In a series RLC circuit, what happens to the total impedance when the circuit is at resonance? (2022)
A.
It is minimum
B.
It is maximum
C.
It is equal to R
D.
It is equal to L
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Solution
At resonance in a series RLC circuit, the total impedance is minimum and is equal to the resistance (R) of the circuit.
Correct Answer: C — It is equal to R
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Q. In a simple cubic lattice, how many atoms are present in one unit cell? (2019)
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Solution
In a simple cubic lattice, there is 1 atom per unit cell (1/8 atom from each of the 8 corners).
Correct Answer: A — 1
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