Question

When an electron and a proton are placed in an electric field ___________.
A) The electric forces acting on them are equal in magnitude as well as direction.
B) Only the magnitudes of forces are the same.
C) Acceleration produced in them is the same.
D) Magnitude of acceleration produced in them is the same.

Answer 1

To answer this question, we should know that when a charged particle is kept in an electric field, an electric force is exerted on it due to the electric field. When another charged particle is placed in the same electric field, an electric force is also produced by it. Also, coulomb's force is exerted by them on each other. The magnitude of these forces and their direction depends on the amount of charge i.e, magnitude, and the net charge on the particle respectively.

Complete step by step solution:
We all know that an electron is an atomic particle that has a unit negative charge and negligible mass and a proton is an atomic particle with a unit positive charge and an atomic mass of up to $1.6 \times {10^{ - 27}}kg$.
Therefore, from this, we can deduce that a proton has an equal opposite charge compared to an electron. The only difference is that protons are heavier than electrons.

According to our question, when an electron and a proton are placed in an electric field, due to their opposite polarity they attract each other with an electrical force that is equal in magnitude. But the direction of the force will be opposite due to their opposite charge. The proton will experience a force in the direction of the electric field and the electron will experience a force in the direction antiparallel to the electric field.

The acceleration caused due to this force will be different on the electron and proton due to the different masses of the electron and proton.

In conclusion, the correct option is B.

Note: Here, the direction of force is opposite however, the magnitude is the same. Therefore it should not be confusing, as the charge on both are of equal magnitude but the nature is different. As force is a vector quantity, that is, it is defined by direction as well as magnitude. Therefore, in this question, the direction highly matters. We need to remember that the force on the positive charge is in the direction of the electric field and in the case of negative charge the force is opposite to the electric field.