Free Circuit Analysis MCQs with Answers

• A. decrease
• B. increase
• C. remains unchanged
• D. become zero

Explanation: Bakelite acts as a dielectric with relative permittivity greater than that of air.

• A. 0.024 F
• B. 0.12 F
• C. 0.6 F
• D. 0.8 F

Explanation: Using C = Q/V gives C = 0.24/10 = 0.024 F. This is equivalent to 24 mF, so option a is correct.

• A. 5 uF
• B. 30 uF
• C. 45 uF
• D. 50 uF

Explanation: For three identical capacitors in series, the equivalent capacitance is one-third of a single capacitor: C = 15/3 = 5 μF.

• A. away from the charge
• B. towards the charge
• C. both A. and (6)
• D. none of the above

Explanation: The electric field direction is defined as the force on a positive test charge, so a positive source charge produces a field directed…

• A. 400 N/C
• B. 600 N/C
• C. 800 N/C
• D. 1200 N/C

Explanation: For a point charge, electric field varies inversely with the square of distance: E₂ = 200(4/2)² = 800 N/C.

• A. always parallel
• B. always at 90°
• C. inclined at any angle 0
• D. none of the above

Explanation: The electric field points in the direction of greatest potential decrease, while an equipotential surface has no potential change along…

• A. 60 N
• B. 30 N
• C. 40 N
• D. 15 N

Explanation: Coulomb force varies inversely as the square of distance. Doubling the distance makes the force one-fourth, so 120/4 = 30 N.

• A. electrons
• B. protons
• C. neutrons
• D. electric field

Explanation: A charged body produces an electric field around it, and another charge experiences force when placed in that field.

• A. low permittivity
• B. high permittivity
• C. permittivity same as that of air
• D. permittivity slightly more than that of air

Explanation: Capacitance is C = εA/d, so increasing the dielectric permittivity increases the charge stored for the same voltage.

• A. Current
• B. Efficiency of the circuit
• C. Power in the load resistance
• D. Voltage across the load resistance

Explanation: For a source with internal resistance, maximum power transfer occurs when the load resistance equals that internal resistance.

• A. current is maximum
• B. current is minimum
• C. impedance is maximum
• D. voltage across C is minimum

Explanation: At series resonance, the inductive and capacitive reactances cancel, leaving minimum impedance.

• A. increases with the decrease of capacitance and decrease of resistance
• B. increases with the decrease of capacitance and increase of resistance
• C. increases with the increase of capacitance and decrease of resistance
• D. increase with increase of capacitance and increase of resistance

Explanation: For a capacitive circuit, the time constant is τ = RC. It increases when both resistance and capacitance increase, so option d fits.

• A. actual power is zero
• B. reactive power is zero
• C. apparent power is zero
• D. none of above is zero

Explanation: In a purely inductive circuit, current lags voltage by 90°, so average or actual power is zero even though reactive power and apparent…

• A. increases with increase of inductance and decrease of resistance
• B. increases with the increase of inductance and the increase of resistance
• C. increases with the decrease of inductance and decrease of resistance
• D. increases with decrease of inductance and increase of resistance

Explanation: The inductive time constant is τ = L/R. Therefore, it increases with larger inductance and smaller resistance.

• A. depends upon the magnitude of R
• B. depends upon the magnitude of L
• C. depends upon the magnitude of C
• D. depends upon the magnitude of R, Land C

Explanation: At series resonance, inductive and capacitive reactances cancel, leaving impedance equal to R.

• A. R only
• B. L only
• C. C only
• D. LorC
• E. R,LorC

Explanation: The series resonance frequency is f_r = 1/(2π√LC), so it can be changed by changing either L or C.

• A. R/C
• B. RC2
• C. RC
• D. R2C

Explanation: For a series RC circuit, the time constant is the product of resistance and capacitance: τ = RC. Hence option c is correct.

• A. applied voltage decreases but current increases
• B. applied voltage increases but current decreases
• C. both applied voltage and current increase
• D. both applied voltage and current decrease

Explanation: In a pure inductor, current lags voltage by 90° and energy is returned during the remaining part of the cycle.

• A. Inductance
• B. Capacitance
• C. Conductance
• D. Resistance

Explanation: A capacitor opposes sudden changes in voltage because its current is i = C dv/dt, so an abrupt voltage change would require an…

• A. zero
• B. lagging
• C. leading
• D. unity

Explanation: An electric bulb is predominantly resistive, so its voltage and current are in phase. Its power factor is therefore unity.