Free Capacitors MCQs with Answers
63 Capacitors MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Capacitors store electric charge and energy in an electric field between conductors. Work includes capacitance, the relation Q = CV, dielectric materials, charging and discharging, energy formulas, and combinations of capacitors in series and parallel. Electric potential difference is needed to understand why charge and stored energy change.
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- A. the charge stored per unit potential difference across the capacitor
- B. the energy stored per unit charge
- C. the charge multiplied by the voltage
- D. the potential difference per unit charge
Explanation: C equals Q over V, measured in farads, and it depends only on the geometry of the plates and the dielectric between them, not on how much…
Correct answer: the charge stored per unit potential difference across the capacitor- A. increasing the plate separation
- B. decreasing the plate area
- C. increasing the plate area and inserting a dielectric
- D. increasing the applied voltage
Explanation: Capacitance is proportional to the area and to the relative permittivity of the dielectric, and inversely proportional to the separation…
Correct answer: increasing the plate area and inserting a dielectric- A. the sum of the individual capacitances
- B. less than the smallest of them
- C. the reciprocal of the sum of the reciprocals
- D. always equal to one of them
Explanation: Parallel capacitors share the same voltage and their plate areas effectively add, so the capacitances add directly.
Correct answer: the sum of the individual capacitances- A. QV
- B. half CV squared
- C. CV
- D. half QC
Explanation: The factor of one half appears because the voltage rises from zero to V as the capacitor charges, so the average voltage during the…
Correct answer: half CV squared- A. increase
- B. decrease, because the capacitance rises while the charge is fixed
- C. stay the same
- D. become zero
Explanation: With the capacitor disconnected the charge cannot change, and since V equals Q over C, raising the capacitance must lower the voltage.
Correct answer: decrease, because the capacitance rises while the charge is fixed- A. Remains same
- B. Brightness increases
- C. Brightness decreases
- D. No light
Explanation: Glass acts as a dielectric, increasing the capacitor's capacitance. Since capacitive reactance Xc = 1/(2πfC), the reactance decreases and…
Correct answer: Brightness increases- A. 32Ω
- B. 62Ω
- C. 50Ω
- D. 100Ω
Explanation: Capacitive reactance is Xc = 1/(2πfC) = 1/(2 x 3.14 x 50 Hz x 100 x 10^-6 F) ≈ 31.8 Ω, which is about 32 Ω.
Correct answer: 32Ω- A. 0.9sec
- B. 15 sec
- C. 1.5 x 10^5sec
- D. 0.9 x 10^2sec
Explanation: The required charge is Q = CV = (30 x 10^-6 F)(300 V) = 0.009 C. With constant current I = 10 mA = 0.010 A, the charging time is t = Q/I =…
Correct answer: 0.9sec- A. 4 KV
- B. 16 kV
- C. 54 kV
- D. 8 kV
Explanation: The expression relating the energy stored in a capacitor with respect to potential difference and capacitance is : E = ½ CV² 24 = ½…
Correct answer: 4 KV- A. Q = 20 uC and E = 50 ueV
- B. Q = 10 uC and E = 100 eV
- C. Q = 10 uC and E = 500 eV
- D. Q = 20 uC and E = 100 uJ
- E. Q = 10 uC and E = 200 uJ
Explanation: The energy stored in a capacitor is given by the formula:E = 1/2 × C × V2where E is the energy stored, C is the capacitance, and V is the…
Correct answer: Q = 20 uC and E = 100 uJ- A. ½ CV2
- B. ⅓ CV2
- C. CV2
- D. None of these
Explanation: The energy stored in a capacitor is given by the formula:U = 1/2 CV2where U is the energy stored in the capacitor, C is the capacitance of…
Correct answer: ½ CV2- A. All the three in series
- B. All the three in parallel
- C. Two in series and one in parallel
- D. Two in parallel and one in series
Explanation: If two capacitors are connected in series and the resulting combination is in parallel with the third capacitor,Two capacitors in series…
Correct answer: Two in series and one in parallel- A. 0.63qo
- B. 0.51qo
- C. 0.37qo
- D. 0.9qo
Explanation: In an RC circuit, the time constant (τ) is defined as the time it takes for the charge to reach approximately 63.2% of its maximum value.
Correct answer: 0.63qo- A. Double
- B. Quadruple
- C. Half
- D. One Fourth
Explanation: The energy stored in a capacitor is given by the formula:U = (1/2) * C * V²Where:U is the energy storedC is the capacitanceV is the…
Correct answer: Quadruple- A. Energy = ½ CV
- B. Energy = ½ C2V
- C. Energy = ½ CV2
- D. Energy = ½ C/V
Explanation: The graph of the charge on a capacitor against the voltage across it shows a linear line starting from origin marking a direct…
Correct answer: Energy = ½ CV2- A. ½ µF
- B. 3/2 µF
- C. 5/2 µF
- D. 4/3 µF
- E. 2 µF
Explanation: Recall that the effective capacitance of capacitors in series is the reciprocal of the sum of reciprocals of individual capacitors (just…
Correct answer: 4/3 µF- A. Decreases
- B. Increases
- C. Remains constant
- D. Zero
Explanation: ○The strength of the electric field is reduced due to the presence of dielectric.
Correct answer: Increases- A. To deposit 63% of the equilibrium charge
- B. To deposit 36% of the equilibrium charge
- C. To deposit 63 times of the equilibrium charge
- D. To deposit 36 times of the equilibrium charge
Explanation: q = q°(1-e-t/RC), in the equation RC is the time constant which denotes the time it takes for "63.2% of the charge to be deposited" on the…
Correct answer: To deposit 63% of the equilibrium charge- A. 2.43 x 10^-4 J
- B. 4.86 x 10^-4 J
- C. 2.43 x 10^-2 J
- D. 4.86 x 10^-2 J
Explanation: E = CV^2/2 = QV/2 = 0.5 X 18 X 2.7x10^-6 = 2.43x10^-4 J As this is a numerical so only one option is correct.
Correct answer: 2.43 x 10^-4 J- A. All three capacitors are in series
- B. Two capacitors are in series, one in parallel
- C. Two capacitors are in parallel, one in series
- D. All three capacitors are in parallel
Explanation: When capacitors are connected in parallel, the equivalent capacitance is the sum of the individual capacitances.
Correct answer: All three capacitors are in parallelCapacitors MCQs: common questions
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