When does a piece of matter have a “charge?”

All matter in the universe is made up of atom. Every atom is made up of tiny particles called electrons, protons and neutrons. Generally the number of protons and electrons are equal and the atom is in neutral state.

An entire atom becomes electrically charged when the number of electrons and protons are not equal, means when some electrons are taken from the atom or are given to an atom. The extra electrons or protons begin to attract the protons or electrons in other atoms.

Example: When a glass rod is rubbed with a piece of silk cloth the rod becomes positively charged while the cloth has a negative charge. As shown in the figure below.