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 2 of 42
- A. 50 N/C
- B. 100 N/C
- C. 200 N/C
- D. 400 N/C
Explanation: This is the option marked correct in the official UHS answer key. Field intensity is directly proportional to the charge producing it, so…
Correct answer: 400 N/C- A. Increases by a factor of 2.5
- B. Decreases by a factor of 2.5
- C. Increases by a factor of 5
- D. Decreases by a factor of 5
Explanation: Relative permittivity appears in the denominator of Coulomb's law, so inserting a medium of relative permittivity 2.5 reduces the force to…
Correct answer: Decreases by a factor of 2.523. If the surface charge density of an infinite sheet increases by 25%, the electric field intensity:
- A. Increases by 25%
- B. Increases by 50%
- C. Decreases by 25%
- D. Remains the same
Explanation: The field of an infinite charged sheet is the surface charge density divided by twice the permittivity, so it is directly proportional to…
Correct answer: Increases by 25%- A. Midway between them
- B. Along the perpendicular bisector
- C. Close to either charge
- D. At infinity
Explanation: At the midpoint the two fields are equal in magnitude and opposite in direction, so they cancel exactly and the resultant is zero, which…
Correct answer: Midway between them- A. Two times
- B. Four times
- C. Eight times
- D. Sixteen times
Explanation: Doubling both charges multiplies the numerator of Coulomb's law by four, and halving the separation divides the denominator by four since…
Correct answer: Sixteen times- 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: 0.9sec29. When two charges are placed in water then the Coulomb force between them reduces to _____________?
- A. 1/2 times
- B. 1/3 times
- C. 1/78 times
- D. 1/58 times
Explanation: In a medium, Coulomb force becomes Fmedium = Fair/εr; water has a relative permittivity of about 78, so Fwater ≈ Fair/78, or 1/78 times…
Correct answer: 1/78 times- A. F
- B. F/2
- C. F/4
- D. F/8
Explanation: Initially, the magnitude of the force is proportional to |(+2Q)(-Q)| = 2Q².
Correct answer: F/8- A. - 1.6 x 10^-12 coulomb
- B. - 1.6 x 10^-13 coulomb
- C. - 1.6 × 10 -18 coulomb
- D. - 1.6 × 10 coulomb
Explanation: Each added electron has charge -1.6 x 10^-19 coulomb. For 1,000,000 electrons, total charge = 1,000,000 x (-1.6 x 10^-19 coulomb) = -1.6 x…
Correct answer: - 1.6 x 10^-13 coulomb- A. 100 C m-2
- B. 200 C m-2
- C. 300 C m-2
- D. 400 C m-2
Explanation: The cube side is 5 cm = 0.05 m, and its total surface area is 6a² = 6(0.05 m)² = 0.015 m².
Correct answer: 400 C m-2- A. Field theory
- B. Acoustics
- C. Hydro dynamic
- D. Optics
Explanation: Field theory studies physical fields and their properties, and gravitational physics treats the gravitational field produced by mass.
Correct answer: Field theory- A. Decreases
- B. increases
- C. remains the same
- D. becomes zero
Explanation: The potential energy of two charges is U = kq1q2/r. For two electrons, q1q2 is positive, so reducing their separation r makes U increase.
Correct answer: increases35. The electric P.E of an electron in an orbit at a distance rn from the positive charge_____________?
- A. Ke2/rn
- B. Ke2/rn2
- C. ÀKe2/rn
- D. ÀKe2/rn2
Explanation: The electric potential energy of two opposite charges is U = kq1q2/r. For an electron and a positive charge, q1q2 is negative, giving U =…
Correct answer: ÀKe2/rn- A. Kinetic energy increases
- B. P.E. between them increases
- C. P.E. between them decreases
- D. P.E. between tem does not change
Explanation: The electric potential energy of two like charges is U = kq1q2/r. Since both particles are protons and r decreases, their positive…
Correct answer: P.E. between them increases- 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