Free Coulomb's Law MCQs with Answers
21 Coulomb's Law MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Coulomb's law gives the electrostatic force between two point charges in terms of their magnitudes, separation and the medium between them. Questions involve attraction and repulsion, the inverse square relationship, superposition of forces and vector direction, which must not be confused with the electric field produced by a charge.
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- A. the product of the charges and inversely proportional to the distance between them
- B. the product of the charges and inversely proportional to the square of the distance
- C. the sum of the charges and the square of the distance
- D. the square of the product of the charges
Explanation: The inverse square dependence means doubling the separation quarters the force, exactly as in Newton's law of gravitation.
Correct answer: the product of the charges and inversely proportional to the square of the distance2. If the distance between two point charges is halved, the electrostatic force between them becomes
- A. half
- B. double
- C. four times
- D. one quarter
Explanation: Force varies as one over the square of the separation, so halving the distance multiplies the force by four.
Correct answer: four times- A. four times greater
- B. one quarter
- C. unchanged
- D. twice as great
Explanation: The medium appears in the denominator of Coulomb's law, so a relative permittivity of 4 reduces the force to a quarter of its vacuum…
Correct answer: one quarter- 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 2.5- 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 times6. 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. F/4
- B. F/2
- C. 2F
- D. 4F
Explanation: The force between two charges in a medium is given by Coulomb's law, which states that the force is inversely proportional to the…
Correct answer: F/4- A. 1.48 N (attractive)
- B. 1.48 N (repulsive)
- C. 2.96 (repulsive)
- D. Zero
Explanation: The charges after adding -5C become:Q1 = +5-5 = 0CQ2 = -12-5 = -17CUsing formulaF= kq1q2/r21.48 = 9(109) (0)(17)/r2Since one charge is 0C…
Correct answer: Zero- A. Gases
- B. Metals
- C. Liquids
- D. Insulators
Explanation: Insulators (D): Insulators, particularly those specifically designed as dielectric materials, have high dielectric constants.
Correct answer: Insulators- A. two-third of the previous value.
- B. one-third of the previous value.
- C. one-fourth of the previous value.
- D. three-fourth of the previous value.
Explanation: When the distance between two identical charges is doubled, the force of repulsion between them decreases by a factor of 1/2^2 = 1/4.
Correct answer: one-fourth of the previous value.- A. Increase
- B. Decrease
- C. Remain constant
- D. Vary unpredictably
Explanation: When a dielectric slab is inserted between two point charges, it polarizes in response to the electric field created by the charges.
Correct answer: Decrease- A. Gauss's law
- B. Newton's law
- C. Ohm's law
- D. Coulomb's law
Explanation: The explanation for this question will be added soon.
Correct answer: Coulomb's law- A. Non-conservative
- B. Conservative
- C. It depends on the shape of the charge
- D. None of these options are correct
Explanation: The electrostatic, or Coulomb's, force is conservative, which means that the work done on q is independent of the path taken.
Correct answer: Conservative- A. Reduces the electrostatic force
- B. Increases the electrostatic force
- C. Does not change electrostatic force
- D. Doubles the electrostatic force
Explanation: Fvacum = 1/4πϵ0 × q1q2/r In presence of dielectricFmedium = 11/4πϵ0ϵr × q1q2/rFmedium= Fvacum/ ϵrThis clearly shows that by putting…
Correct answer: Reduces the electrostatic force- A. 1.6 x 10^-19 C
- B. 9 x 10^9 C
- C. 9.1 x 10^-31 C
- D. 1.6 x 10^-27 C
Explanation: The smallest unit charge is that of the electron or a proton in magnitude i.e. 1.6x10(-19)
Correct answer: 1.6 x 10^-19 C- A. 1 x 10^-9 C
- B. 1 x 10^9 C
- C. 2 x 10^-9C
- D. 4 x 10^-9 C
Explanation: From coulomb's law we knowF=Kq1q2/r²Rearranging the equation, we get:q2=Fxr²/Kxq1 =2x9/9x10⁹x1 =2x10-⁹C Ans
Correct answer: 2 x 10^-9C- A. F-1=1/4πe0 x q1q2/r2 x r
- B. F = 1/4πe0 x q1q2/r2 x r
- C. F-1 = 1/4πe x q1q2/r2 x r
- D. F = 1/4πe x q1q2/r2 x r
Explanation: According to the expression of coulomb's law, the magnitude of Coulomb's force is directly proportional to the product of two point…
Correct answer: F = 1/4πe0 x q1q2/r2 x r- A. Lost electrons
- B. Lost protons
- C. Gained protons
- D. Gained electrons
Explanation: When a neutral body becomes positively charged, it means it has lost electrons.
Correct answer: Lost electrons20. The Ratio of electro force between two protons to that between two electrons is of the order of:
- A. 1042
- B. 1039
- C. 1036
- D. 1
Explanation: d) 1This option suggests that the ratio of the electrostatic force between two protons to that between two electrons is 1.
Correct answer: 1Coulomb's Law MCQs: common questions
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