Q. In an AC circuit, if the current lags the voltage by 30 degrees, what is the power factor? (2023)
-
A.
0.866
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B.
0.5
-
C.
1
-
D.
0.707
Solution
The power factor (PF) is given by cos(θ). If θ = 30 degrees, PF = cos(30°) = √3/2 ≈ 0.866.
Correct Answer: A — 0.866
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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)
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A.
12.56Ω
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B.
37.68Ω
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C.
75.36Ω
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D.
100Ω
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
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B.
It decreases
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C.
It remains constant
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D.
It becomes zero
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 0.5, what is the angle φ between the voltage and current? (2019)
-
A.
30 degrees
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B.
60 degrees
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C.
90 degrees
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D.
45 degrees
Solution
The power factor (cosφ) is 0.5, which corresponds to an angle φ of 60 degrees.
Correct Answer: B — 60 degrees
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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°
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B.
53.13°
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C.
60°
-
D.
45°
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 total impedance? (2020)
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A.
10 ohms
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B.
20 ohms
-
C.
√(10² + 20²)
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D.
30 ohms
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 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
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 10Ω and the inductive reactance is 20Ω, what is the total impedance? (2020)
-
A.
10Ω
-
B.
20Ω
-
C.
√(10² + 20²)
-
D.
30Ω
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 total current is 5A and the total voltage is 100V, what is the impedance? (2021)
-
A.
20Ω
-
B.
25Ω
-
C.
30Ω
-
D.
15Ω
Solution
Impedance Z = V/I = 100V/5A = 20Ω.
Correct Answer: B — 25Ω
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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
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B.
1200 W
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C.
800 W
-
D.
1000 W
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 120 V and the current is 10 A, what is the power factor if the real power is 600 W? (2021)
-
A.
0.5
-
B.
0.6
-
C.
0.8
-
D.
1.0
Solution
Power factor = Real Power / (Voltage × Current) = 600 / (120 × 10) = 0.5.
Correct Answer: C — 0.8
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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
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
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
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C.
50 V
-
D.
141.4 V
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
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 given by V(t) = V0 sin(ωt), what is the expression for the current if the circuit is purely inductive? (2023)
-
A.
I(t) = I0 sin(ωt)
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B.
I(t) = I0 sin(ωt - π/2)
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C.
I(t) = I0 cos(ωt)
-
D.
I(t) = I0 cos(ωt + π/2)
Solution
In a purely inductive circuit, the current lags the voltage by 90 degrees (π/2 radians). Therefore, I(t) = I0 sin(ωt - π/2).
Correct Answer: B — I(t) = I0 sin(ωt - π/2)
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Q. In an AC circuit, if the voltage is given by V(t) = V_0 sin(ωt), what is the expression for the current if the circuit is purely inductive? (2023)
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A.
I(t) = I_0 sin(ωt)
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B.
I(t) = I_0 sin(ωt - π/2)
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C.
I(t) = I_0 cos(ωt)
-
D.
I(t) = I_0 cos(ωt + π/2)
Solution
In a purely inductive circuit, the current lags the voltage by 90 degrees (or π/2 radians). Therefore, I(t) = I_0 sin(ωt - π/2).
Correct Answer: B — I(t) = I_0 sin(ωt - π/2)
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Q. In an AC circuit, if the voltage is given by V(t) = V₀ sin(ωt), what is the expression for the current through a capacitor? (2022)
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A.
I(t) = C dV/dt
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B.
I(t) = V₀ sin(ωt)
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C.
I(t) = V₀ cos(ωt)
-
D.
I(t) = V₀ sin(ωt)/R
Solution
The current through a capacitor is given by I(t) = C dV/dt. For V(t) = V₀ sin(ωt), the current can be derived from this expression.
Correct Answer: A — I(t) = C dV/dt
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Q. In an AC circuit, if the voltage is V(t) = 120 sin(ωt), what is the RMS voltage? (2017)
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A.
120 V
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B.
60 V
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C.
84.85 V
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D.
100 V
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 average power consumed is given by which formula? (2022)
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A.
P = VI
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B.
P = VI cos(φ)
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C.
P = V²/R
-
D.
P = I²R
Solution
The average power (P) consumed in an AC circuit is given by P = VI cos(φ), where φ is the phase angle between voltage and current.
Correct Answer: B — P = VI cos(φ)
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Q. In an AC circuit, the current lags behind the voltage by 90 degrees in which type of circuit? (2020)
-
A.
Resistive
-
B.
Inductive
-
C.
Capacitive
-
D.
RLC
Solution
In an inductive circuit, the current lags behind the voltage by 90 degrees.
Correct Answer: B — Inductive
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Q. In an AC circuit, the current lags the voltage by 90 degrees in which of the following components? (2020)
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A.
Resistor
-
B.
Capacitor
-
C.
Inductor
-
D.
Transformer
Solution
In an inductor, the current lags the voltage by 90 degrees.
Correct Answer: C — Inductor
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Q. In an AC circuit, the current lags the voltage by 90 degrees in which type of circuit? (2020)
-
A.
Resistive
-
B.
Capacitive
-
C.
Inductive
-
D.
RLC
Solution
In an inductive circuit, the current lags the voltage by 90 degrees.
Correct Answer: C — Inductive
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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)
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 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
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, what is the phase difference between voltage and current in a purely inductive circuit? (2021)
-
A.
0 degrees
-
B.
90 degrees
-
C.
180 degrees
-
D.
270 degrees
Solution
In a purely inductive AC circuit, the current lags the voltage by 90 degrees.
Correct Answer: B — 90 degrees
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Q. In an AC circuit, what is the relationship between the average power and the RMS voltage? (2023)
-
A.
P = V_rms²/R
-
B.
P = V_peak²/R
-
C.
P = V_rms/R
-
D.
P = V_peak/R
Solution
The average power (P) in an AC circuit is given by P = V_rms²/R, where R is the resistance.
Correct Answer: A — P = V_rms²/R
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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
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
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
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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