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Asked in GSEB Board March 2020 · Coulomb's law and superposition
Idea: both forces are inverse-square, so the distance cancels in the ratio.
Fₑ=(ke²)/(r²) and F_g=(Gmₑmₚ)/(r²)
(Fₑ)/(F_g)=(ke²)/(Gmₑmₚ)=((9×10⁹)(1.6×10⁻¹⁹)²)/((6.67×10⁻¹¹)(9.1×10⁻³¹)(1.67×10⁻²⁷))
Numerator: 2.30×10⁻²⁸. Denominator: 1.01×10⁻⁶⁷.
(Fₑ)/(F_g)≈2.3×10³⁹ - the ratio NCERT quotes as 2.4×10³⁹, and the only option with the right power of ten.
The electric force is about 10³⁹ times the gravitational one, which is why gravity plays no part in holding an atom together.
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