Free Electrostatics MCQs with Answers
831 Electrostatics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Electrostatics describes forces between charges through Coulomb's law, electric fields and field intensity, then uses electric potential to measure energy per unit charge. Capacitors store charge and electrical energy, with capacitance depending on geometry and dielectric material, not simply on the amount of charge present.
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Read the Electrostatics notesFree MDCAT chapter notes with key terms831 questions · page 14 of 42
- A. kQ/R
- B. kQ/R²
- C. Zero
- D. kQ/(2R)
Explanation: For a charged conductor, the potential at the surface is V = kQ/R, and at infinity, V = 0. Thus, the potential difference is kQ/R.
Correct answer: kQ/R- A. Doubles
- B. Halves
- C. Increases but doesn't double
- D. Remains unchanged
Explanation: The system acts as two capacitors in series: one with dielectric (C₁ = 2ε₀A/(d/2)) and one without (C₂ = ε₀A/(d/2)).
Correct answer: Increases but doesn't double- A. kQ/r²
- B. Zero
- C. kQ/R₁ ²
- D. kQ/R₂ ²
Explanation: Inside a neutral conducting shell, the electric field is zero due to electrostatic shielding.
Correct answer: Zero- A. 3.6 × 10⁴ V
- B. 1.8 × 10⁴ V
- C. Zero
- D. 5.4 × 10⁴ V
Explanation: Potential is a scalar sum. Distance from each charge to (2, 0) is √(2² + 2²) = 2√2 m.
Correct answer: 3.6 × 10⁴ V- A. Q²/(2ε₀A)
- B. Q²/(ε₀A)
- C. Q²/(4πε₀d²)
- D. Zero
Explanation: The force between capacitor plates is F = Q²/(2ε₀A), derived from the energy stored U = Q²/(2C) and F = -dU/dd, where C = ε₀A/d.
Correct answer: Q²/(2ε₀A)- A. 4.2 × 10⁶ m/s
- B. 8.4 × 10⁶ m/s
- C. 2.1 × 10⁶ m/s
- D. 5.9 × 10⁶ m/s
Explanation: Using energy conservation, work done by the field equals kinetic energy gained: qEΔx = (1/2)mv².
Correct answer: 4.2 × 10⁶ m/s- A. kQ/(2R²)
- B. kQ/(√2R²)
- C. kQ/(2√2R²)
- D. Zero
Explanation: For a charged ring, the electric field on the axis at distance x is E = kQx/(R² + x²)^(3/2).
Correct answer: kQ/(2√2R²)- A. 80 V
- B. 40 V
- C. 60 V
- D. 120 V
Explanation: In series, Ceq = (3 × 6)/(3 + 6) = 2 μF. Charge Q = CeqV = 2 × 10⁻⁶ × 120 = 2.4 × 10⁻⁴ C.
Correct answer: 80 V- A. Increases by a factor of 4
- B. Decreases by a factor of 4
- C. Remains unchanged
- D. Becomes zero
Explanation: With constant charge, E = Q/(ε₀εrA). Inserting a dielectric with εr = 4 reduces E by a factor of 4, as the electric field is inversely…
Correct answer: Decreases by a factor of 4- A. d/3
- B. d/√2
- C. d/(1 + √2)
- D. 2d/3
Explanation: Let the point be at distance x from +2q. The fields due to +2q and -q cancel: k(2q)/x² = kq/(d - x)².
Correct answer: d/(1 + √2)- A. 1.5C
- B. 2C
- C. C
- D. 4C/3
Explanation: The system acts as two capacitors in parallel: one with air (C₁ = ε₀A/(2d)) and one with dielectric (C₂ = 2ε₀A/(2d)).
Correct answer: 4C/3- A. 6.75 × 10⁻³ J
- B. -6.75 × 10⁻³ J
- C. Zero
- D. 3.38 × 10⁻³ J
Explanation: Work done is W = qΔV, where ΔV is the potential difference. Potential at r = 4 m is V₁ = k(-3 × 10⁻⁶)/4, and at r = 2 m is V₂ = k(-3 ×…
Correct answer: -6.75 × 10⁻³ J- A. σ/(2ε₀)
- B. σ/ε₀
- C. σ/(4πε₀)
- D. Zero
Explanation: Using Gauss's law, the electric field due to an infinite charged sheet is E = σ/(2ε₀), independent of distance from the sheet, due to…
Correct answer: σ/(2ε₀)- A. Φ = 1/ε₀ q
- B. Φ = 3/ε₀ q
- C. Φ = 6/ε₀ q
- D. Φ = 1/6ε₀ q
Explanation: The total flux through the cube is q/ε₀, and it is evenly divided among the six faces due to symmetry.
Correct answer: Φ = 1/6ε₀ q- A. EQ = ER
- B. EQ < ER
- C. VQ > VR
- D. VQ < VR
Explanation: The electric potential at a point is inversely related to the distance from a positive charge.
Correct answer: VQ > VR- A. q
- B. qd/r
- C. -qr/d
- D. zero
Explanation: This is the correct answer. The method of images shows that the induced charge on the sphere is proportional to the charge and inversely…
Correct answer: -qr/d- A. 18.5 V
- B. 13.5 V
- C. 11.5 V
- D. 6.5 V
Explanation: When a dielectric slab of thickness 3 mm and dielectric constant K = 10 is inserted between the plates of a capacitor, the effective…
Correct answer: 11.5 V- A. C
- B. 2C
- C. 3C
- D. 4C
Explanation: The insertion of a thin conducting plate halfway between the plates effectively creates two capacitors in series, doubling the capacitance…
Correct answer: 4C- A. 100V
- B. 50V
- C. 150V
- D. 200V
Explanation: The change in angles and kinetic energy corresponds to this potential difference.
Correct answer: 50V- A. Electric intensity
- B. Electric flux
- C. Electric current
- D. Electric potential
Explanation: Electric current is the flow of charge through a conductor per unit time.
Correct answer: Electric current