Coulomb’s Law (Forces Between Two Point Charges, Forces Between Multiple Charges... ) NEET Questions

Physics - Electrostatics
Coulomb’s Law (Forces Between Two Point Charges, Forces Between Multiple Charges... )

Coulomb’s Law (Forces Between Two Point Charges, Forces Between Multiple Charges... ) MCQ Questions


7.

Spheres A and B have charges q and q', respectively, and are separated by a distance r. The force between them is F. Sphere A is then touched by an identical uncharged sphere C, so that A gets a charge q/2, and sphere B is touched by an identical uncharged sphere D, so that B gets a charge q'/2. The distance between A and B is then reduced to r/2. The new force F' is:

A.

F' = 2F

B.

F' = 4F

C.

F' = F (same as original force)

D.

F' = F/4

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ANSWER :

C. F' = F (same as original force)

8.
In vector form, Coulomb's law for the force on charge q₂ due to charge q₁ is written as F₂₁ = (1/4πε₀)(q₁q₂/r²₂₁) r̂₂₁ where r̂₂₁ is a unit vector from q₁ to q₂. If q₁ and q₂ are both positive, F₂₁ is directed:
A.
Along r̂₂₁ (away from q₁, in the direction from q₁ to q₂) — repulsive force
B.
Perpendicular to the line joining the charges
C.
Along the line joining the charges but could be either direction regardless of sign
D.
Along −r̂₂₁ (toward q₁) — attractive force
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ANSWER :
A. Along r̂₂₁ (away from q₁, in the direction from q₁ to q₂) — repulsive force
9.
The vector form of Coulomb's law automatically satisfies Newton's Third Law because:
A.
Newton's Third Law does not apply to electrostatic forces
B.
The forces add up to zero only when the charges are equal
C.
F₁₂ = F₂₁ (equal magnitude and same direction)
D.
F₁₂ = −F₂₁: the force on q₁ due to q₂ is equal in magnitude and opposite in direction to the force on q₂ due to q₁
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ANSWER :
D. F₁₂ = −F₂₁: the force on q₁ due to q₂ is equal in magnitude and opposite in direction to the force on q₂ due to q₁
10.
Coulomb's law in vector form uses the notation r̂₂₁. What does r₂₁ represent?
A.
The vector from q₁ to q₂, i.e., r₂₁ = r₂ − r₁, where r₁ and r₂ are position vectors of q₁ and q₂
B.
The vector from q₂ to q₁
C.
The position vector of the midpoint between the two charges
D.
The unit vector along the electric field direction
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ANSWER :
A. The vector from q₁ to q₂, i.e., r₂₁ = r₂ − r₁, where r₁ and r₂ are position vectors of q₁ and q₂
11.

The ratio of electric force to gravitational force between an electron and a proton at any distance r is approximately:

A.

Fe/Fg ≈ 2.4 × 10³⁹ — the electric force is enormously stronger than gravity

B.

Fe/Fg≈ 10¹⁰ — electric force is moderately stronger

C.

Fe/Fg ≈ 1 — they are roughly equal

D.

Fe/Fg ≈ 10⁻³⁹ — gravity is stronger

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ANSWER :

A. Fe/Fg≈ 2.4 × 10³⁹ — the electric force is enormously stronger than gravity

12.

Two protons inside a nucleus (separation ≈ 10⁻¹⁵ m) experience both Coulomb repulsion and gravitational attraction. The approximate values are:

A.

Fe ≈ Fg ≈ 10⁻¹⁰ N (roughly equal)

B.

Fe ≈ 230 N (repulsive Coulomb), Fg ≈ 1.9 × 10⁻³⁴ N (attractive gravity) — Coulomb force dominates enormously

C.

Fg ≈ 230 N (gravity dominates at nuclear scale)

D.

Fe ≈ 1.9 × 10⁻³⁴ N, FG ≈ 230 N

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ANSWER :

B. Fe ≈ 230 N (repulsive Coulomb), Fg ≈ 1.9 × 10⁻³⁴ N (attractive gravity) — Coulomb force dominates enormously

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