Electric Charge - Practice Questions & MCQ

Electric charge: It is observed that glass rods rubbed with wool or silk repel each other and attracts lighter objects like paper. Similarly, silk and woollen cloth also repel each other and glass rod and wool attracts each other. Similarly, plastic rod rubbed with cats fur repel each other. The plastic rod attracts a glass rod and repels wool and silk. From the above observation, it was concluded by scientists that by rubbing glass rod, silk, wool and plastic rods are electrified or charged.

The charge is the property associated with the matter due to which it produces and experiences the electrical and magnetic effect. 

From observations, the scientist has concluded that plastic rod has accrued a kind of charge and the glass rod has accrues another kind of charge. That is the electric charge are of two types, namely positive charge and negative charge. A body is called to be positively charged when the body which loses electrons and the negatively charged when the body gains electrons. 

Electric charge is a scalar quantity and its SI unit is Coulomb represented as C.  C= 1 ampere-second. The dimension of charge is [AT]. 

Like charges repel each other (glass rods rubbed with wool or silk repel each other) and unlike charges attract each other (glass rod and wool attract each other).

Point charge: If the size of charged bodies is too small compared to the distance between them we treat them as a point charge.                                                    

Properties of charge:
1. Additivity: If a system contains n charge $q_1, q_2, q_3 \ldots \ldots q_n$, then the total charge of the system is $q_1+q_2+\ldots . . q_n$.
2. The charge is conserved: Charge can be neither created nor destroyed. When we rub a glass rod with silk there is a transfer of charge and not creation. The total charge of an isolated system is always conserved.
3. The charge is independent of the velocity of the particle. I.e The charge is non-relativistic.
4. Quantization: Charge on a body will be some integral multiple of $e$, where $e$ is the charge of the electron.

$
e=1.6 \times 10^{-19} \mathrm{C}
$