Physics · Electric Charges And Fields · NEET
For charged particles like electrons and protons, yes - the electric force is enormously larger (about 10^36 to 10^39 times) than the gravitational force between the same two particles. But this only applies when charges are present. Neutral bodies have no net electric force, so only gravity acts. That is why gravity, though weak, controls planets and stars: large objects are electrically neutral overall, but their mass keeps adding up.
Compare the two constants. Coulomb's constant k is about 9 x 10^9 N m^2 C^-2, while the gravitational constant G is about 6.67 x 10^-11 N m^2 kg^-2. The electric constant is about 10^20 times larger. On top of that, charge values (like 1.6 x 10^-19 C) produce far more force per unit than the tiny masses of an electron or proton. The result is the huge ratio you see in NCERT.
The mathematical form is identical: F = k q1 q2 / r^2 for electric and F = G m1 m2 / r^2 for gravity. Both depend on the product of the source quantities (charge or mass) and on 1/r^2. The differences are: (1) the constant k is much bigger than G, (2) charge can be positive or negative so electric force can attract OR repel, while gravity is always attractive, and (3) electric force depends on the medium but gravity does not.
Because big objects are electrically neutral. Positive and negative charges nearly cancel, so the net electric force between a planet and a star is essentially zero. Mass, however, never cancels - it only adds. So over stars, planets and galaxies, gravity accumulates and dominates, even though particle-for-particle it is the weaker force.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
About 2.4 x 10^39. The electric force is roughly 10^39 times stronger than the gravitational force between an electron and a proton, as given in NCERT.
About 1.3 x 10^36. It is smaller than the electron-proton case because a proton has more mass than an electron, so the gravitational force is a little larger.
Yes. Coulomb's law (F = k q1 q2 / r^2) and Newton's law of gravitation (F = G m1 m2 / r^2) both fall off as 1/r^2. Doubling the distance makes each force one-fourth.
Yes. Charges can be positive or negative, so the electric force can attract or repel. Mass is always positive, so gravity is always attractive - it never repels.
Yes for the electric force. Placing charges in a medium (dielectric constant K) reduces the electric force by a factor K. Gravitational force does not depend on the medium, so in a dielectric the ratio drops but the electric force usually still stays far larger.
