Question

If a body is charged by rubbing it, its weight ____________.

• A. Remains precisely constant
• B. Increases slightly
• C. Decreases slightly
• D. May increase or decrease slightly

Answer 1

The correct option is D

May increase or decrease slightly

Explanation for correct option:

Option (D):

1. When a body is charged by rubbing, an exchange of charge takes place.
2. The charge is determined by the charge of an electron.
3. We know the charge of an electron $e=1.6\times {10}^{-19}C$ and the mass of an electron is $9.1\times {10}^{-31}kg$.
4. Hence, when an exchange of charge takes place, the weight of the body might vary by factors of $9.1\times {10}^{-31}kg$.
5. When positive charges are induced, it will lose a small amount of mass due to losing some electrons, and if negative charges are induced, it will gain a small amount of mass due to gaining some electrons.

Explanation for incorrect option:

Option (A):

1. Since the exchange of charge takes place, the mass of the body might vary by factors of $9.1\times {10}^{-31}kg$.
2. Therefore, the weight of the body will not be constant.

Option (B):

1. Since the exchange of charge takes place, the mass of the body might vary by factors of $9.1\times {10}^{-31}kg$.
2. When positive charges are induced, it will lose a small amount of mass, and if negative charges are induced, it will gain a small amount of mass.
3. Hence, the weight may decrease as well.

Option (C):

1. Since the exchange of charge takes place, the mass of the body might vary by factors of $9.1\times {10}^{-31}kg$.
2. When positive charges are induced, it will lose a small amount of mass, and if negative charges are induced, it will gain a small amount of mass.
3. Thus the weight may increase as well.

Hence, option D is the correct answer.