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 5 of 30
- A. 2 L I2
- B. 4 L I2
- C. 8 L I2
- D. 16 L I2
Explanation: The energy stored in an inductor is given by the formula E = 1/2 L I2. When the current 'I' increases by a factor of 4, the new energy…
Correct answer: 16 L I2- A. inductor
- B. capacitor
- C. impedance
- D. modulation
Explanation: The correct answer is 'impedance.' In a circuit, impedance is the combination of resistance (which opposes the flow of current) and…
Correct answer: impedance- A. Zero
- B. Large
- C. Small
- D. Varying unpredictably
Explanation: In an alternating current circuit, the current through a capacitor increases with frequency because the capacitive reactance (which…
Correct answer: Large- A. 314.2 V
- B. 220.0 V
- C. 154.0 V
- D. 110.0 V
Explanation: The correct answer is Option A: 314.2 V. The peak value of an AC voltage is √2 times the RMS value.
Correct answer: 314.2 V- A. I and II
- B. I and IV
- C. II and III
- D. III and IV
Explanation: The correct answer is Option C: II and III. In alternating current (AC) circuits, inductors store energy in magnetic fields, and…
Correct answer: II and III- A. Io
- B. √2 Io
- C. Io / √2
- D. 2 Io
Explanation: The correct formula for finding the root mean square (r.m.s.) current for an alternating current (AC) signal is Io / √2, as indicated in…
Correct answer: Io / √2- A. Resistor
- B. Inductor
- C. Capacitor
- D. Transistor
Explanation: The correct answer is Transistor. Transistors are primarily used for amplification and switching purposes rather than directly controlling…
Correct answer: Transistor- A. Zero.
- B. Large.
- C. Small.
- D. Undetermined.
Explanation: In an AC circuit, the current through a capacitor depends on the capacitive reactance, which is inversely proportional to the frequency.
Correct answer: Large.- A. Option A: The vectors for IC and IR are in phase.
- B. Option B: The vector for IC leads the vector for IR by 90 degrees.
- C. Option C: The vectors for IC and IR are out of phase by 180 degrees.
- D. Option D: The vectors for IC and IR are perpendicular.
Explanation: In an RC circuit, the current through the capacitor (IC) leads the current through the resistor (IR) by 90 degrees due to the capacitive…
Correct answer: Option B: The vector for IC leads the vector for IR by 90 degrees.- A. Resistance.
- B. Impedance.
- C. Capacitance.
- D. Conductance.
Explanation: The correct answer is impedance. In an alternating current (AC) circuit, impedance is the term used to describe the ratio of the root mean…
Correct answer: Impedance.- A. Zero.
- B. More.
- C. Less.
- D. Infinite.
Explanation: Capacitive reactance (XC) is given by the formula XC = 1/(2πfC), where f is the frequency and C is the capacitance.
Correct answer: Zero.- A. The current will be zero.
- B. The current will be large.
- C. The current will be small.
- D. The current will be undetermined.
Explanation: In an AC circuit, a capacitor's reactance decreases as the frequency increases.
Correct answer: The current will be large.- A. twice the peak value
- B. (1/√2 ) times the peak value
- C. half the peak value
- D. equal to the peak value
Explanation: The root-mean-square (rms) value of an alternating current is given by Irms =Ipeak/√2 .
Correct answer: (1/√2 ) times the peak value- A. 2A
- B. 2√2 A
- C. √2 A
- D. zero
Explanation: To find the rms value of the given current, we need to use the relationship between the rms value and the peak value of an AC current.
Correct answer: √2 A- A. double
- B. half
- C. √2 A
- D. four times
Explanation: As the frequency increases, the impedance of the resistor (which is effectively its resistance in the context of AC circuits) remains…
Correct answer: double- A. 0
- B. ω⋅C
- C. 1/ω⋅C1
- D. ∞
Explanation: Explanation: In a DC (direct current) circuit, the frequency ω is considered to be 0, because DC does not vary with time.
Correct answer: ∞- A. the current leads the voltage
- B. the current and voltage are in phase
- C. the current lags behind the voltage
- D. any one of the above may be true depending upon the value of the resistance
Explanation: In a purely resistive AC circuit, such as when an AC source is connected across a resistor, the current and voltage are in phase with each…
Correct answer: the current and voltage are in phase98. An LCR series circuit contains L=8 H,C=0.5μF, and R=100Ω. The resonant frequency of the circuit is
- A. 1000/π Hz
- B. 250/π Hz
- C. 500/π Hz
- D. 125/π Hz
Explanation: The resonant frequency of an LCR series circuit is given by the formula f0 =1/2πLC .
Correct answer: 1000/π Hz- A. minimum
- B. maximum
- C. infinity
- D. zero
Explanation: Impedance in a Series LCR Circuit:Impedance (Z) in a series LCR circuit represents the total opposition to the flow of alternating current…
Correct answer: minimum- A. remain same
- B. constantly reverses
- C. always positive
- D. always negative
Explanation: As the charging potential alternates, the charge on the antenna also alternates in polarity.
Correct answer: constantly reverses