Free Alternating Current MCQs with Answers
592 Alternating Current MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Alternating current varies periodically, so phase relationships become essential when current passes through a resistor, capacitor or inductor. The chapter distinguishes resistance from capacitive and inductive reactance, explains phase lead and lag, and connects changing electric and magnetic fields with the production and properties of electromagnetic waves.
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Read the Alternating Current notesFree MDCAT chapter notes with key terms592 questions · page 21 of 30
- A. The circuit is dissipating maximum power
- B. The circuit may or may not be dissipating maximum power
- C. The circuit is not dissipating any power
- D. None of the above
Explanation: In an AC circuit, the power factor is a measure of how effectively the current is being converted into useful work.
Correct answer: The circuit is dissipating maximum power- A. Increases
- B. Decreases
- C. Same
- D. None
Explanation: When soft iron is placed inside a solenoid, it increases the solenoid's magnetic field strength, thereby increasing the inductance of the…
Correct answer: Decreases- A. Inductance
- B. Capacitance
- C. Resistance
- D. All of the above
Explanation: The power factor (cos φ) in an AC circuit measures the phase difference between voltage and current, and it depends on the presence of…
Correct answer: All of the above- A. The impedance is minimum
- B. The voltage across the inductor (VL) is greater than the applied voltage
- C. The voltage across the capacitor (VC) is greater than the applied voltage
- D. All of the above
Explanation: In an RLC series AC circuit at resonance, the impedance is at its minimum.
Correct answer: The impedance is minimum- A. Two
- B. Three
- C. Four
- D. Infinite
Explanation: The resonance frequency of an LC circuit is determined by the formula f = 1 / (2π√(LC)), where 'L' is the inductance and 'C' is the…
Correct answer: Infinite- A. Doubled
- B. Quadrupled
- C. Tripled
- D. Halved
Explanation: In an RLC circuit at resonance, the resonance frequency is determined by the formula f = 1 / (2π√(LC)).
Correct answer: Halved- A. 4L, C/4
- B. 2C, 2L
- C. 4L, 4C
- D. 2L, 4C
Explanation: Resonance in an RLC circuit occurs when the inductive reactance (XL = ωL) is equal to the capacitive reactance (XC = 1/ωC).
Correct answer: 4L, C/4- A. Inductive
- B. Capacitive
- C. Positive
- D. None
Explanation: In an RLC series AC circuit, the behavior of the circuit is determined by the relative magnitudes of the capacitive and inductive…
Correct answer: Capacitive- A. The circuit behaves as a capacitive circuit
- B. Xc > XL
- C. Current leads the voltage
- D. All of the above
Explanation: In an RLC series circuit, when the applied frequency is less than the resonance frequency, the capacitive reactance is greater than the…
Correct answer: All of the above- A. 100%
- B. 50%
- C. 99.9%
- D. 70%
Explanation: In the scenario of maximum power transfer, the load resistance is equal to the source resistance.
Correct answer: 50%- A. Resonance
- B. Not in resonance
- C. Not possible
- D. None of the above
Explanation: The correct answer is Not possible. In an RLC circuit, efficiency is typically maximized at resonance due to minimized impedance, allowing…
Correct answer: Not possible- A. Rheostat
- B. Potential divider
- C. Thermistor
- D. Resistor
Explanation: In AC circuits, a choke coil is used to limit the current without causing a significant loss of energy, thanks to its inductive…
Correct answer: Rheostat- A. Energy stored per cycle
- B. Energy dissipated per cycle
- C. Both energy stored and dissipated per cycle
- D. Power loss
Explanation: The quality factor (Q-factor) of an oscillating system is defined as the ratio of the energy stored to the energy dissipated per cycle.
Correct answer: Both energy stored and dissipated per cycle- A. Zero
- B. ∞
- C. Infinite
- D. Maximum but finite
Explanation: The quality factor, or Q factor, is a measure of how underdamped an oscillator or resonator is, and characterizes a resonator's bandwidth…
Correct answer: Zero415. Q factor depends on:
- A. Resistance (R)
- B. Frequency
- C. Inductance (L)
- D. All of the above
Explanation: The Q factor, or quality factor, of an RLC circuit is a measure of how underdamped the circuit is and is defined as the ratio of the…
Correct answer: All of the above- A. Q factor
- B. Inductance
- C. Both A and B
- D. R
Explanation: The sharpness of resonance in an electrical circuit is primarily determined by the Q factor, which is influenced by both inductance (L)…
Correct answer: Both A and B- A. L and R
- B. E and L
- C. E and R
- D. L, R, and E
Explanation: In a series R-L circuit connected to a DC battery, the final value of the current is determined by the battery's emf (E), the resistance…
Correct answer: L, R, and E- A. 15/√2 A
- B. 5/√3 A
- C. 5/√5 A
- D. 15 A
Explanation: To find the effective current when DC and AC are combined:DC current = 5 AAC current = 10sin(ωt)10/sin(omega t) → RMS = 10/√2 =5√2…
Correct answer: 5/√3 A- A. Equal to V1 + V2 + V3
- B. Equal to V1 - V2 + V3
- C. More than V1 + V2 + V3
- D. none of these
Explanation: In a series L-C-R AC circuit, the voltages across the inductor (L), capacitor (C), and resistor (R) have phase differences due to their…
Correct answer: none of these- A. ωL/R
- B. 1/ωRC
- C. √LC
- D. L/R
Explanation: The quality factor, or Q-factor, of an RLC circuit is a dimensionless parameter that describes how underdamped the circuit is and its…
Correct answer: ωL/R