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 29 of 30
- A. 94.2
- B. 1.57
- C. 157
- D. 9,421
Explanation: Inductive reactance is the opposition offered by the inductor in the AC circuit to the flow of AC current.
Correct answer: 157- A. resistive circuit
- B. capacitive circuit
- C. inductive circuit
- D. resonant circuit
Explanation: At low frequencies, the series circuit is capacitive as Xc>Xl, but at higher frequencies, the series circuit is inductive as Xl>Xc.
Correct answer: capacitive circuit- A. CRO (Cathode Ray Oscilloscope)
- B. Diode
- C. Transistor
- D. Radio
Explanation: The correct answer is CRO (Cathode Ray Oscilloscope). A CRO is designed to visually display the waveform of electrical signals, allowing…
Correct answer: CRO (Cathode Ray Oscilloscope)- A. 125W
- B. 160W
- C. 250W
- D. 500W
Explanation: To find the mean power developed by the current in the resistive load, we first calculate the peak value of the current, which is 3.53.
Correct answer: 125W- A. In-phase
- B. Current leads voltage by 90o
- C. Voltage leads current by 90o
- D. Current leads voltage by 180o
Explanation: It can be seen that the phase at O is zero and the phase at the upper maximum is π/2.
Correct answer: Current leads voltage by 90o- A. Leads the voltage by one-half of a cycle
- B. Leads the voltage by one-fourth of a cycle
- C. Lags the voltage by one-half of a cycle
- D. Is in phase with the voltage
Explanation: In a purely resistive circuit, the current and voltage are in phase with each other.
Correct answer: Is in phase with the voltage- A. Effect in charging battery
- B. Effect in charging capacitor
- C. Heating effect through a resistance
- D. Effect passing through an inductance
Explanation: The correct option is Effect in charging battery. Both AC and DC can charge a battery, but typically AC is converted to DC for this…
Correct answer: Effect in charging battery- A. Volt-second/ampere
- B. Volt/second
- C. Ohm
- D. Ampere volt/second
Explanation: The unit "henry" (H) is used to measure inductance in the International System of Units (SI).
Correct answer: Volt-second/ampere- A. 1
- B. Greater than 1
- C. Less than 1 but greater than zero
- D. Zero
Explanation: In a purely inductive circuit, the average power dissipated is zero. This is because the current and voltage are 90 degrees out of phase…
Correct answer: Zero- A. Increase
- B. Initially increase than decrease
- C. Remain the same
- D. Decrease
Explanation: When the iron core is removed from a coil, transforming it into an air-cored coil, the inductance of the coil will decrease.
Correct answer: Decrease- A. Pure capacitive circuit
- B. Pure inductive circuit
- C. RLC series AC circuit at resonance
- D. Both (A) & (8) are true
Explanation: In a pure capacitive circuit, the alternating voltage and current have a phase difference of 90 degrees with each other.
Correct answer: Pure capacitive circuit- A. Gamma rays
- B. UV
- C. Microwave
- D. X-rays
Explanation: In the given electromagnetic spectrum it can be seen that wavelength increases from gamma rays towards radio waves and frequency…
Correct answer: Microwave- A. Modulated waves
- B. Carrier waves
- C. Standing waves
- D. Rectified waves
Explanation: Such waveforms are used in modulation. Modulation is the process of converting data into radio waves by adding information to an…
Correct answer: Carrier waves- A. Alpha rays
- B. X_rays
- C. Cosmic rays
- D. Beta rays
Explanation: Cosmic rays are high-energy particles that come from outside our solar system.
Correct answer: Cosmic rays- A. Stationary charges
- B. Charges moving with uniform speed
- C. Accelerating charges
- D. All of the above
Explanation: Electromagnetic waves are produced when charges undergo acceleration. Acceleration of charges creates changing electric and magnetic…
Correct answer: Accelerating charges- A. rectification
- B. amplification
- C. modulation
- D. magnification
Explanation: Modulation is the process of combining low-frequency signals with high-frequency carrier waves to convert data into radio waves.
Correct answer: modulation- A. 1x10
- B. 3.0 x 10^7
- C. 1x10¹0
- D. 1 x 10^13
Explanation: We know that v = f λ v --- = f λ (placing values) 3 × 10⁸ f = ------------------ 3 × 10⁻³ × 10⁻² f = 1 × 10¹³
Correct answer: 1 x 10^13- A. x rays > i.r. > u.v. > visible
- B. x rays > u.v. > visible > i.r.
- C. u.v. > x rays > visible > i.r.
- D. i.r. > visible > x rays > u.v.
Explanation: In the electromagnetic spectrum, the energy of photons is inversely proportional to their wavelength.
Correct answer: x rays > u.v. > visible > i.r.- A. Parallel
- B. Anti-parallel
- C. Perpendicular
- D. None of the above
Explanation: In electromagnetic waves, the electric and magnetic fields are oriented perpendicular to each other and to the direction of wave…
Correct answer: Perpendicular- A. Speed
- B. Wavelength
- C. Frequency
- D. All of the above
Explanation: Electromagnetic waves travel at a constant speed of approximately 3 × 10^8 m/s in a vacuum.
Correct answer: Speed