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 22 of 30
- A. V²/ωL
- B. I²Lω
- C. I²R
- D. V²/ωC
Explanation: In a series RLC circuit at resonance, the inductive and capacitive reactances cancel each other out, leaving only the resistance to…
Correct answer: I²R- A. The generator frequency should be reduced
- B. Another capacitor should be added in parallel to the first
- C. The iron core of the inductor should be removed
- D. The dielectric in the capacitor should be removed
Explanation: The resonant frequency of an LCR circuit is given by the formula f=1/2π√LC, where L is the inductance and C is the capacitance.
Correct answer: Another capacitor should be added in parallel to the first- A. Voltage V
- B. Inductance L
- C. Capacitance C
- D. V2/L
Explanation: In a series LCR circuit, the voltage V is analogous to the driving force F(t) in mechanics.
Correct answer: Voltage V- A. Material medium
- B. Vacuum
- C. Oscillating electric and magnetic field
- D. All
Explanation: Electromagnetic waves can propagate through a vacuum and do not need a material medium for their transmission.
Correct answer: All- A. Magnetic field
- B. Electric field
- C. An e.m.f
- D. Pressure radiant
Explanation: Maxwell's hypothesis postulates that a changing electric field generates a magnetic field.
Correct answer: Magnetic field- A. 0 V
- B. 9.56 V
- C. 10.6 V
- D. 19.1 V
Explanation: The average value of a sinusoidal voltage over a complete cycle is 0 V.
Correct answer: 0 V- A. 1
- B. Greater than 1
- C. Less than 1
- D. Zero
Explanation: In a purely inductive circuit, the current lags the voltage by 90 degrees, resulting in a power factor of cos(90°) = 0.
Correct answer: Zero- A. 2
- B. 4√2
- C. 4/√2
- D. 2/√2
Explanation: The root mean square (r.m.s.) value of an alternating current is derived from its peak value using the formula Irms = Ipeak / √2.
Correct answer: 4/√2- A. 1/2π√LC
- B. 2π√LC
- C. 1/2πLC
- D. 1/2π√L
Explanation: The resonance frequency of an LCR circuit is given by the formulaf = 1/2π√(LC)This formula arises from the balance of inductive and…
Correct answer: 1/2π√LC- A. 0°
- B. 90°
- C. 60°
- D. 180°
Explanation: The correct answer is 90°. In a purely inductive AC circuit, the current lags the voltage by 90 degrees.
Correct answer: 90°- A. X-rays
- B. Gamma rays
- C. Cathode rays
- D. Infrared rays
Explanation: Cathode rays EM waves travel with a constant velocity of 3.00x10⁸ ms-1 in vacuum.
Correct answer: Cathode rays- A. λm > λx > λv
- B. λm > λv > λx
- C. λv > λx > λm
- D. λv > λm > λx
Explanation: The electromagnetic spectrum is generally divided into seven regions, in order of decreasing wavelength and increasing energy and…
Correct answer: λm > λv > λx- A. Oscillating electric field is along X-axis and oscillating magnetic field is along Y-axis
- B. Oscillating electric field is along Z-axis and oscillating magnetic field is along X-axis
- C. Both oscillating electric and magnetic fields are along Y-axis, but phase difference between them is 90°
- D. Both oscillating electric and magnetic fields are mutually perpendicular in arbitrary directions
Explanation: An electromagnetic wave is propagating along Y-axis, then oscillating electric field is along Z-axis and oscillating magnetic field is…
Correct answer: Oscillating electric field is along Z-axis and oscillating magnetic field is along X-axis- A. Kinetic energy
- B. Magnetic field
- C. Electric field
- D. Both (b) and (c)
Explanation: In an electromagnetic wave, the average value of the electric field or magnetic field is zero, because electromagnetic waves are sinusoids…
Correct answer: Both (b) and (c)- A. Polarization
- B. Interference
- C. Reflection
- D. Diffraction
Explanation: Only transverse waves can be polarized. Longitudinal waves cannot be polarized.
Correct answer: Polarization- A. 100 km
- B. 200 km
- C. 300 km
- D. 400 km
Explanation: This is the following solution:Wavelength = c/v=3×10⁸ms-¹/1000s-¹=3×10⁵=300Km
Correct answer: 300 km- A. Ground waves
- B. X-ray
- C. α − rays
- D. Sky waves
Explanation: The waves which can travel directly along surface of the earth are known as ground waves.
Correct answer: Ground waves- A. Radius of the earth
- B. Height of the antenna
- C. Radius of the earth and also height of the antenna
- D. None of above
Explanation: The distance upto which T.V. signals D=√ 2hR. Where R =radius of the earth and h = height of the antenna.
Correct answer: Radius of the earth and also height of the antenna- A. Radio wave and micro-wave region
- B. The micro-wave and visible region
- C. The visible and ultra violet region
- D. The ultra violet and the X-ray region
Explanation: The infrared (IR) spectrum lies between visible light and the micro-waves on the electromagnetic spectrum.
Correct answer: The micro-wave and visible region- A. Radio wave
- B. Ultrasonic wave
- C. Microwave
- D. Audible wave
Explanation: Radio waves have a least frequency that is about 10 Hz.
Correct answer: Radio wave