Suppose the charge of a proton and an electron differ slightly. One of them is -e, the other is (e + Δe). If the net of electrostatic force and gravitational force between two hydrogen atoms placed at a distance d (much greater than atomic size) apart is zero, then Ae is of the order of [Given mass of hydrogen m = 1.67 × 10^-27 kg]

Calculation:
The electrostatic force between two charges is given by Coulomb’s law:

F_e = (k × |q₁ × q₂|) / r²

Where:

• k is Coulomb’s constant (9 × 10⁹ N·m²/C²),
• q₁ and q₂ are the charges on the particles,
• r is the distance between the particles.

The gravitational force between two masses is given by Newton's law of gravitation:

F_g = (G × m₁ × m₂) / r²

Where:

• G is the gravitational constant (6.67 × 10⁻¹¹ N·m²/kg²),
• m₁ and m₂ are the masses of the particles,
• r is the distance between the particles.

The forces cancel when:

F_e = F_g

Solving the equation, we find that the charge difference Δe (the difference between the proton and electron charge) is of the order of 10^-20 C.

Correct Answer: Option 4 - 10^-20 C