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 12 of 42
- A. 2V
- B. 5V
- C. 10V
- D. 20V
Explanation: First, find the electric field strength: E = F/q = 2000 N / 2 C = 1000 N/C.
Correct answer: 10V- A. 2.5×10⁻³ C
- B. 10⁻³ C
- C. 10³ C
- D. 4×10³ C
Explanation: The charge (Q) stored on a capacitor is given by the formula Q = CV. Q = (5 × 10⁻⁶ F) × (200 V) = 1000 × 10⁻⁶ C = 10⁻³ C.
Correct answer: 10⁻³ C- A. 6.25×10¹⁸
- B. 1.6×10⁻¹⁹
- C. 6.25x10²¹
- D. 1.6×10⁻²⁷
Explanation: The charge of one electron is approximately 1.6 × 10⁻¹⁹ C. To find the number of electrons in one coulomb, we divide the total charge by…
Correct answer: 6.25×10¹⁸- A. 240 μC
- B. 480 μC
- C. 720 μC
- D. 360 μC
Explanation: In parallel, each capacitor has the same voltage (60 V). Charge on the 8 μF capacitor is Q = CV = (8 × 10⁻⁶)(60) = 4.8 × 10⁻⁴ C = 480 μC.
Correct answer: 480 μC- A. 10⁻⁸ C
- B. 2 × 10⁻⁸ C
- C. 10⁻⁹ C
- D. 5 × 10⁻⁹ C
Explanation: Potential at the surface is V = kQ/R. Solving for Q, Q = VR/k = (900)(0.1)/(9 × 10⁹) = 10⁻⁹ C.
Correct answer: 10⁻⁹ C- A. 8.8 × 10¹³ m/s²
- B. 1.76 × 10¹⁴ m/s²
- C. 1.24 × 10¹⁴ m/s²
- D. Zero
Explanation: Acceleration is a = qE cosθ/m. For an electron (q = 1.6 × 10⁻¹⁹ C, m = 9.1 × 10⁻³¹ kg), E = 10³ N/C, θ = 45°, a = (1.6 × 10⁻¹⁹)(10³)…
Correct answer: 1.24 × 10¹⁴ m/s²- A. Q only
- B. V only
- C. U only
- D. Q and U only
Explanation: When circuit elements are connected in parallel, they are connected across the same two points in the circuit.
Correct answer: V only- A. The charge will flow from A to B
- B. The charge will flow from B to A
- C. No flow of charge will occur
- D. Both A and B are possible
Explanation: The potential of a sphere is V = kQ/r. Sphere A (smaller radius) has a higher initial potential than sphere B.
Correct answer: The charge will flow from A to B- A. 16 x 10⁻⁵ J
- B. 32 x 10⁻⁶ J
- C. 3.2 x 10⁻⁴ J
- D. 16 x 10⁻⁴ J
Explanation: The work done to charge a capacitor is equal to the energy stored, U = Q²/(2C).
Correct answer: 3.2 x 10⁻⁴ J- A. A scalar quantity
- B. A vector quantity
- C. A dimensionless quantity
- D. Always positive quantity
Explanation: Electric potential represents energy per unit charge and does not have a direction associated with it, only a magnitude.
Correct answer: A scalar quantity- A. Cmed/Cvac
- B. Cvac/Cmed
- C. Cmed + Cvac
- D. Cmed×Cvac
Explanation: Relative permittivity (or dielectric constant) is a dimensionless factor that describes how much a dielectric material increases the…
Correct answer: Cmed/Cvac- A. F
- B. 8F
- C. 4F
- D. 16F
Explanation: The force is F ∝ (q₁q₂)/r². The new force F' will have a factor of (2×2) in the numerator from doubling the charges and a factor of (1/2)²…
Correct answer: 16F- A. E
- B. E²
- C. 1/E²
- D. E³
Explanation: The energy density (energy per unit volume) stored in an electric field is given by the formula u = (1/2)ε₀E².
Correct answer: E²- A. 14.4 x 10⁴ volt
- B. 7.2 x 10⁵ volt
- C. 7.2 x 10⁴ volt
- D. 14.4 x 10⁸ volt
Explanation: The charge of the nucleus is Q = 50e. The potential is V = kQ/r = k(50e)/r. V = (9×10⁹)(50 × 1.6×10⁻¹⁹) / (10⁻¹²) = 7.2 × 10⁴ V.
Correct answer: 7.2 x 10⁴ volt- A. 10V
- B. 20V
- C. -10V
- D. -20V
Explanation: Potential (V) is defined as work done (W) per unit charge (q), so V = W/q. In this case, V = 100 J / (-5 C) = -20 V.
Correct answer: -20V- A. The electric field is zero, but the potential is non-zero
- B. The electric field is non-zero, but the potential is zero
- C. Both the electric field and potential are zero
- D. Both the electric field and potential are non-zero
Explanation: The potential is a scalar and sums to V = k(2q)/r + k(-q)/r + k(-q)/r = 0.
Correct answer: The electric field is non-zero, but the potential is zero- A. 20 N/C
- B. 500 N/C
- C. 5 N/C
- D. 250 N/C
Explanation: For parallel plates, the uniform electric field is E = V/d. E = 10 V / 0.02 m = 500 V/m.
Correct answer: 500 N/C- A. 1:2
- B. 1:4
- C. 2:1
- D. 4:1
Explanation: The kinetic energy gained is equal to the change in potential energy, (1/2)mv² = qV. Thus, speed v = √(2qV/m).
Correct answer: 1:2- A. It would decrease by a factor of 4
- B. It would decrease by a factor of 2
- C. It would remain unchanged
- D. It would increase by a factor of 2
Explanation: The force F ∝ (q₁q₂)/r². The new force F' will have a factor of (2×2)=4 in the numerator and a factor of (2)²=4 in the denominator.
Correct answer: It would remain unchanged240. In bringing an electron towards another electron, the electrostatic potential energy of the system:
- A. Increases
- B. Remains the same
- C. Decreases
- D. Becomes zero
Explanation: Since two electrons have like (negative) charges, they repel each other.
Correct answer: Increases