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 current lags the voltage by 30 degrees, what is the type of load?
-
A.
Resistive
-
B.
Inductive
-
C.
Capacitive
-
D.
None of the above
Solution
If the current lags the voltage, it indicates an inductive load, as inductors cause the current to lag behind the voltage.
Correct Answer: B — Inductive
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Q. In an AC circuit, if the current lags the voltage by 30 degrees, what type of circuit is it?
-
A.
Resistive
-
B.
Inductive
-
C.
Capacitive
-
D.
None of the above
Solution
If the current lags the voltage, it indicates an inductive circuit, where the current phase is behind the voltage phase.
Correct Answer: B — Inductive
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Q. In an AC circuit, if the current lags the voltage by 30 degrees, what type of load is present?
-
A.
Resistive
-
B.
Inductive
-
C.
Capacitive
-
D.
None of the above
Solution
If the current lags the voltage, it indicates the presence of an inductive load, as inductors cause the current to lag behind the voltage.
Correct Answer: B — Inductive
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Q. In an AC circuit, if the current lags the voltage by 45 degrees, what is the type of load?
-
A.
Resistive
-
B.
Inductive
-
C.
Capacitive
-
D.
None of the above
Solution
If the current lags the voltage, it indicates an inductive load, as inductors cause the current to lag behind the voltage.
Correct Answer: B — Inductive
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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
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 doubled, what happens to the inductive reactance?
-
A.
It doubles
-
B.
It halves
-
C.
It remains the same
-
D.
It quadruples
Solution
Inductive reactance (X_L) is given by X_L = 2πfL. If the frequency (f) is doubled, X_L also doubles.
Correct Answer: B — It halves
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Q. In an AC circuit, if the frequency is doubled, what happens to the reactance of an inductor?
-
A.
Doubles
-
B.
Halves
-
C.
Remains the same
-
D.
Quadruples
Solution
The reactance of an inductor is given by X_L = 2πfL. If frequency is doubled, reactance halves.
Correct Answer: B — Halves
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Q. In an AC circuit, if the frequency is increased, what happens to the capacitive reactance? (2020)
-
A.
It increases
-
B.
It decreases
-
C.
It remains constant
-
D.
It becomes zero
Solution
Capacitive reactance XC = 1/(2πfC) decreases as frequency f increases.
Correct Answer: B — It decreases
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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
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 between voltage and current?
-
A.
30 degrees
-
B.
60 degrees
-
C.
90 degrees
-
D.
45 degrees
Solution
The power factor is cos(θ). If PF = 0.5, then θ = cos^(-1)(0.5) = 60 degrees.
Correct Answer: B — 60 degrees
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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
-
B.
60 degrees
-
C.
90 degrees
-
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°
-
B.
53.13°
-
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 power factor is 1, what type of load is present?
-
A.
Inductive
-
B.
Capacitive
-
C.
Resistive
-
D.
Reactive
Solution
A power factor of 1 indicates a purely resistive load.
Correct Answer: C — Resistive
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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
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 apparent power? (2022)
-
A.
120 W
-
B.
1200 W
-
C.
1000 VA
-
D.
100 VA
Solution
Apparent power S = V * I = 120 V * 10 A = 1200 VA.
Correct Answer: C — 1000 VA
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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
-
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)
-
B.
I(t) = I0 sin(ωt - π/2)
-
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)
-
A.
I(t) = I_0 sin(ωt)
-
B.
I(t) = I_0 sin(ωt - π/2)
-
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) = V_0 sin(ωt), what is the expression for the current through a resistor R?
-
A.
I(t) = (V_0/R) sin(ωt)
-
B.
I(t) = (V_0/R) cos(ωt)
-
C.
I(t) = (R/V_0) sin(ωt)
-
D.
I(t) = (R/V_0) cos(ωt)
Solution
For a resistor, the current is in phase with the voltage. Therefore, I(t) = V(t)/R = (V_0/R) sin(ωt).
Correct Answer: A — I(t) = (V_0/R) sin(ωt)
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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)
-
A.
I(t) = C dV/dt
-
B.
I(t) = V₀ sin(ωt)
-
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)
-
A.
120 V
-
B.
60 V
-
C.
84.85 V
-
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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