Question

When a solid body is negatively charged by friction, it means that the body has
A. Acquired excess of electrons
B.Lost some protons,
C. Acquired some electrons and lost a lesser number of protons,
D. Lost some positive ions.

Answer 1

Electrons are movable while protons are not. Charge at a microscopic level in a body is quantized which means all free charges are integral multiple of a basic unit of charge of an electron/proton represented by 'e'.

Complete answer:
Charge $q$ in a body is given by $q= ne$.
Here, $n$= number of electrons and $e$= $1.6 \times {{10}^{-19}}\,C$
The quantization of charge was first suggested by experimental laws of electrolysis discovered by Faraday and was experimentally demonstrated by Millikan.Positive charge is given by protons present in the nucleus core of the atoms of a solid and negative charge is given by electrons present outside and away from the nucleus.

A body while having equal amounts of both positive and negative charges is said to be electrically neutral. When there is a charge imbalance, a body is said to be charged.The nucleus rests at its position and doesn't move, only the electrons move and get transferred to different bodies when rubbed against each other.

It is due to the presence of excess electrons or lack of electrons as compared to protons in a solid that gives a body positive or negative charge, be it at microscopic level or macroscopic level. The cause of charging is the transfer of electrons from one body to another.So, when a solid body is negatively charged by friction, it means that the body has acquired an excess of electrons as compared to the protons present in the body.

Hence, the correct answer is option A.

Note: A solid body is said to be charged when it attracts or repels another charged body, which can only be achieved with the imbalance of protons and electrons and we know that only electrons are mobile.