All Free Electrical Engineering MCQs with Answers
Every Electrical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
3,143 questions · page 10 of 158
- A. one joule/coulomb
- B. one coulomb/joule
- C. one coulomb
- D. one joule
Explanation: Voltage is defined as energy or work per unit charge, so 1 volt equals 1 joule per coulomb.
Correct answer: one joule/coulomb- A. 0.2 s
- B. 0.4 s
- C. 0.6 s
- D. 0.8 s
Explanation: For an RC circuit, the time constant is τ = RC. With R = 8000 Ω and C = 100 μF, τ = 8000 × 100 × 10⁻⁶ = 0.8 s.
Correct answer: 0.8 s- A. 37, initial
- B. 62, initial
- C. 62, final
- D. 37, final
Explanation: After one time constant, a charging capacitor reaches 1 - e^-1, or about 63.2%, of its final voltage.
Correct answer: 62, final- A. CIR
- B. 1/RC
- C. RC
- D. RIC
Explanation: For a first-order RC charging circuit, the time constant is the product of resistance and capacitance, τ = RC.
Correct answer: RC- A. charge of the charged conductor
- B. capacity of the charged conductor
- C. potential of the charged conductor
- D. all of the above
Explanation: The nearby uncharged conductor becomes charged by electrostatic induction, reducing the potential of the original conductor for the same…
Correct answer: capacity of the charged conductor- A. 5 times smaller than before
- B. 5 times greater than before
- C. 10 times greater than before
- D. 25 times larger than before
Explanation: Coulomb's law gives force proportional to the inverse square of separation, F ∝ 1/r².
Correct answer: 25 times larger than before- A. decreases
- B. increases
- C. reduces to zero
- D. remain unchanged
Explanation: A dielectric polarizes when placed in an electric field, producing an opposing field.
Correct answer: decreases- A. move out of the field of influence of the two charges
- B. remain in stable equilibrium
- C. not be in equilibrium
- D. be in unstable equilibrium
Explanation: At the midpoint, the two repulsive forces on the third charge are equal and opposite, so the net force is zero.
Correct answer: remain in stable equilibrium- A. an electric field
- B. a magnetic field
- C. both A. and (6)
- D. none of the above
Explanation: A stationary electric charge produces an electric field around it. A magnetic field requires moving charge or current, so option b is not…
Correct answer: an electric field- A. Current
- B. Voltage
- C. impedance
- D. None of the above
Explanation: A capacitor resists sudden changes in voltage because its current follows i = C dv/dt; changing its voltage instantly would require…
Correct answer: Voltage- A. 100 kV/m
- B. 10 kV/m
- C. 5 kV/m
- D. 2 kV/m
Explanation: For a uniform electric field between capacitor plates, E = V/d = 400/0.004 = 100,000 V/m. This equals 100 kV/m.
Correct answer: 100 kV/m- A. ceramic plates and one mica disc
- B. insulators separated by a dielectric
- C. silver-coated insulators
- D. conductors separated by an insulator
Explanation: A capacitor stores charge on two conducting plates separated by an insulating dielectric.
Correct answer: conductors separated by an insulator- A. 37
- B. 42
- C. 63
- D. 73
Explanation: In an RC circuit, charging current follows i = I₀e^(-t/RC), so at one time constant it becomes e^-1, or about 36.8% of its initial value.
Correct answer: 37- A. a steady value of applied voltage causes discharge
- B. an increase in applied voltage makes a capacitor charge
- C. decrease in applied voltage makes a capacitor charge
- D. none of the above
Explanation: A capacitor charges when the applied voltage increases, because additional charge is required to establish the higher voltage.
Correct answer: an increase in applied voltage makes a capacitor charge- A. all in series
- B. all in parallel
- C. two in parallel and third in series with this combination
- D. two in series and third in parallel across this combination
Explanation: Putting two capacitors in parallel gives 2C; connecting this combination in series with C gives (2C × C)/(2C + C) = 2C/3.
Correct answer: two in parallel and third in series with this combination- A. Coulomb's square law
- B. Gauss's law
- C. Maxwell's first law
- D. Maxwell's second law
Explanation: Gauss's law relates the total electric flux through a closed surface to the net charge enclosed by that surface.
Correct answer: Gauss's law- A. varying voltage produces the charging and dicharging currents
- B. of high peak value
- C. charging current can flow
- D. discharge current can flow
Explanation: An alternating voltage continually changes the charge on the capacitor, producing alternating charging and discharging currents.
Correct answer: varying voltage produces the charging and dicharging currents- A. volts/coulomb
- B. coulombs/volt
- C. ohms
- D. henry/Wb
Explanation: Capacitance is defined by C = Q/V, so its unit is coulomb per volt, called the farad.
Correct answer: coulombs/volt- A. 20 uF
- B. 30 uE
- C. 40 uF
- D. 50 uF
Explanation: Capacitors in parallel add directly: C = 10 + 10 + 10 = 30 μF. Therefore option b is correct, despite the typographical error in its unit.
Correct answer: 30 uE- A. D.C. only
- B. AC. only
- C. both D.C. as well as A.C.
Explanation: A conventional electrolytic capacitor is polarized, so it is intended for DC or for AC circuits where a suitable DC bias prevents reversal…
Correct answer: D.C. only