Charge is an entity which provides an electric property of the matter. Charge is of two types, positive charge and negative charge. Electrons in an atom consist of negative charge and protons of the atom consist of positive charge. Similar kinds of charges always repel each other and unlike charges attract each other. Charge is a scalar physical quantity. Charge is conserved meaning charge can neither be created nor be destroyed; it can only be transferred from one place to another or from one object to another. The net charge on any system is always constant. All matter is composed of atoms and atoms are composed of three elementary particles, called electrons, protons, and neutrons. Charge is also quantized meaning charge always comes in discrete amounts, and the smallest possible amount of charge that any object could have is \(1.67\times 10^{-19} C\text{.}\) This is the amount of charge on one electron. Whenever an atom gains or loses an electron, the atom is ionized. The ionized atom is always charged. An ion is simply an atom with a net charge. The ion can be positive or negative. If \(q\) is the total negative charge on any object and \(e\) is the charge of electron, then total number of electrons, n on that object can be find using the following equation.
\begin{equation}
q=ne\tag{5.1.1}
\end{equation}
where \(e=1.67\times10^{-19} C.\)
Example5.1.1.
A glass rod is rubbed vigorously with a fur and found that it gained \(+1.67C\) of charge. Calculate how many electrons has the glass rod lost?
Solution.
\begin{align*}
q \amp =ne\\
or, n \amp =\frac{q}{e}\\
or, n \amp =\frac{1.67}{1.67\times10^{-19}}
\end{align*}
