Engineering Entrance
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 thin film interference experiment, what type of interference occurs when light reflects off a denser medium? (2023)
A.
Constructive interference
B.
Destructive interference
C.
No interference
D.
Total internal reflection
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Solution
When light reflects off a denser medium, a phase change of π occurs, leading to destructive interference for certain path differences.
Correct Answer: B — Destructive interference
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Q. In a thin film of oil on water, what color will be seen if the film thickness is such that destructive interference occurs for blue light? (2021)
A.
Red
B.
Green
C.
Blue
D.
Yellow
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Solution
If destructive interference occurs for blue light, the color seen will be the complementary color, which is red.
Correct Answer: A — Red
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Q. In a thin film of oil on water, which color will appear at the center of the pattern if the film is viewed in white light? (2022)
A.
Red
B.
Blue
C.
Green
D.
Yellow
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Solution
At the center of the thin film interference pattern, the color that appears is typically green due to the constructive interference of wavelengths in that range.
Correct Answer: C — Green
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Q. In a vacuum, which of the following travels the fastest?
A.
Sound
B.
Light
C.
Water waves
D.
Radio waves
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Solution
In a vacuum, light travels the fastest at approximately 3 x 10^8 m/s, while sound and water waves require a medium to travel.
Correct Answer: B — Light
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Q. In a zero-order reaction, the rate of reaction is independent of the concentration of the reactants. What is the unit of the rate constant (k) for a zero-order reaction? (2023)
A.
mol/L·s
B.
L^2/mol·s
C.
mol/L
D.
s^-1
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Solution
For a zero-order reaction, the rate is constant and does not depend on the concentration of reactants. The unit of the rate constant (k) is mol/L·s.
Correct Answer: A — mol/L·s
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Q. In a zero-order reaction, the rate of reaction is independent of which of the following? (2023) 2023
A.
Concentration of reactants
B.
Temperature
C.
Presence of a catalyst
D.
All of the above
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Solution
In a zero-order reaction, the rate is constant and does not depend on the concentration of the reactants.
Correct Answer: A — Concentration of reactants
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Q. In an AC circuit, if the frequency is 60Hz and the inductance is 0.2H, what is the inductive reactance? (2021)
A.
12.56Ω
B.
37.68Ω
C.
75.36Ω
D.
100Ω
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Solution
Inductive reactance (XL) = 2πfL = 2π(60)(0.2) ≈ 75.36Ω.
Correct Answer: B — 37.68Ω
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Q. In an AC circuit, if the frequency is increased, what happens to the inductive reactance? (2020)
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
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Solution
Inductive reactance (XL = 2πfL) increases with an increase in frequency.
Correct Answer: A — It increases
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Q. In an AC circuit, if the power factor is 0.8, what is the angle between the voltage and current? (2020)
A.
36.87°
B.
53.13°
C.
60°
D.
45°
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Solution
The angle θ can be found using cos(θ) = power factor. Therefore, θ = cos⁻¹(0.8) ≈ 36.87°.
Correct Answer: B — 53.13°
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Q. In an AC circuit, if the resistance is 10 ohms and the inductive reactance is 20 ohms, what is the impedance? (2020)
A.
10 ohms
B.
20 ohms
C.
√(10² + 20²)
D.
30 ohms
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Solution
The impedance Z = √(R² + XL²) = √(10² + 20²) = √(100 + 400) = √500 = 22.36 ohms.
Correct Answer: C — √(10² + 20²)
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Q. In an AC circuit, if the resistance is 10 ohms and the inductive reactance is 20 ohms, what is the total impedance? (2020)
A.
10 ohms
B.
20 ohms
C.
√(10² + 20²)
D.
30 ohms
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Solution
The total impedance Z = √(R² + XL²) = √(10² + 20²) = √(100 + 400) = √500 = 22.36 ohms.
Correct Answer: C — √(10² + 20²)
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Q. In an AC circuit, if the resistance is 10Ω and the inductive reactance is 20Ω, what is the total impedance? (2020)
A.
10Ω
B.
20Ω
C.
√(10² + 20²)
D.
30Ω
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Solution
The total impedance Z = √(R² + XL²) = √(10² + 20²) = √(100 + 400) = √500 = 22.36Ω.
Correct Answer: C — √(10² + 20²)
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Q. In an AC circuit, if the voltage is 120 V and the current is 10 A with a power factor of 0.8, what is the real power consumed? (2021)
A.
960 W
B.
1200 W
C.
800 W
D.
1000 W
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Solution
Real power P = V * I * power factor = 120 * 10 * 0.8 = 960 W.
Correct Answer: A — 960 W
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Q. In an AC circuit, if the voltage is 120V and the current is 10A with a power factor of 0.8, what is the real power consumed? (2021)
A.
120W
B.
800W
C.
960W
D.
1000W
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Solution
Real power P = V * I * power factor = 120V * 10A * 0.8 = 960W.
Correct Answer: C — 960W
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Q. In an AC circuit, if the voltage is 120V and the current is 10A, what is the power factor if the real power is 600W? (2022)
A.
0.5
B.
0.6
C.
0.8
D.
1.0
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Solution
Power factor = Real Power / (Voltage x Current) = 600 / (120 x 10) = 600 / 1200 = 0.5.
Correct Answer: B — 0.6
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Q. In an AC circuit, if the voltage is given by V(t) = 100 sin(100t), what is the RMS voltage? (2023)
A.
100 V
B.
70.7 V
C.
50 V
D.
141.4 V
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Solution
The RMS voltage is V_rms = V0/√2 = 100/√2 = 70.7 V.
Correct Answer: B — 70.7 V
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Q. In an AC circuit, if the voltage is given by V(t) = 100√2 sin(1000t), what is the peak voltage? (2023)
A.
100 V
B.
100√2 V
C.
200 V
D.
50 V
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Solution
The peak voltage is given by the coefficient of sin, which is 100√2.
Correct Answer: B — 100√2 V
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Q. In an AC circuit, if the voltage is V(t) = 120 sin(ωt), what is the RMS voltage? (2017)
A.
120 V
B.
60 V
C.
84.85 V
D.
100 V
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Solution
RMS voltage V_rms = V_peak / √2 = 120 / √2 = 84.85 V.
Correct Answer: C — 84.85 V
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Q. In an AC circuit, the voltage is given by V(t) = V0 sin(ωt). What is the peak voltage if V0 = 10V? (2021)
A.
5V
B.
10V
C.
15V
D.
20V
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Solution
The peak voltage V0 is given directly in the equation as 10V.
Correct Answer: B — 10V
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Q. In an AC circuit, the voltage is given by V(t) = V0 sin(ωt). What is the peak voltage? (2021)
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Solution
The peak voltage in the equation V(t) = V0 sin(ωt) is V0.
Correct Answer: A — V0
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Q. In an adiabatic process, the relationship between pressure and volume for an ideal gas is given by which equation? (2020)
A.
PV^n = constant
B.
PV = nRT
C.
P1V1 = P2V2
D.
V/T = constant
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Solution
In an adiabatic process, the relationship is given by PV^n = constant, where n is the heat capacity ratio.
Correct Answer: A — PV^n = constant
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Q. In an adiabatic process, the temperature of an ideal gas decreases. What happens to its pressure?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Depends on volume
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Solution
In an adiabatic process, as the temperature decreases, the pressure also decreases due to the ideal gas law.
Correct Answer: B — Decreases
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Q. In an adiabatic process, which of the following is true? (2020)
A.
Heat is absorbed from the surroundings
B.
Heat is released to the surroundings
C.
No heat is exchanged
D.
Temperature remains constant
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Solution
In an adiabatic process, there is no heat exchange with the surroundings, meaning no heat is absorbed or released.
Correct Answer: C — No heat is exchanged
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Q. In an adiabatic process, which of the following remains constant? (2020)
A.
Temperature
B.
Pressure
C.
Internal Energy
D.
Enthalpy
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Solution
In an adiabatic process, there is no heat exchange, so the internal energy remains constant for an ideal gas.
Correct Answer: C — Internal Energy
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Q. In an isochoric process, which of the following remains constant? (2022)
A.
Pressure
B.
Volume
C.
Temperature
D.
Internal Energy
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Solution
In an isochoric process, the volume remains constant.
Correct Answer: B — Volume
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Q. In an isothermal process, the temperature of the gas remains constant. What can be said about the internal energy of an ideal gas? (2020) 2020
A.
It increases
B.
It decreases
C.
It remains constant
D.
It varies with pressure
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Solution
For an ideal gas, the internal energy depends only on temperature. Since the temperature remains constant in an isothermal process, the internal energy also remains constant.
Correct Answer: C — It remains constant
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Q. In an isothermal process, the temperature of the system remains: (2023)
A.
Constant
B.
Increases
C.
Decreases
D.
Varies
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Solution
In an isothermal process, the temperature of the system remains constant.
Correct Answer: A — Constant
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Q. In an RLC circuit, if the resistance is 6Ω, inductive reactance is 8Ω, and capacitive reactance is 4Ω, what is the total impedance? (2021)
A.
10Ω
B.
12Ω
C.
14Ω
D.
16Ω
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Solution
Total impedance Z = √(R² + (XL - XC)²) = √(6² + (8 - 4)²) = √(36 + 16) = √52 ≈ 10Ω.
Correct Answer: B — 12Ω
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Q. In an RLC circuit, if the resistance is increased, what happens to the quality factor (Q)? (2021)
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
The quality factor Q is inversely proportional to resistance. Increasing resistance decreases Q.
Correct Answer: B — Decreases
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