• Charge & Electric Current

Charge and Electric Current

All electric charges produce an electromagnetic field. It causes an attractive or repulsive force interaction with other charges.

Charge

Before we know what electric current is, we should introduce first - charge. Charge is a property of matter that causes it to experience a force when placed in an electromagnetic field. The two basic electrical charges are positive (protons) and negative (electrons). Like charges repel and unlike charges attract each other. The unit of charge is the Coulomb (symbol: C) named after Charles-Augustin de Coulomb. One unit of coulomb is equal to the quantity of electricity which flows when an electric current of one ampere is maintained for one second. Thus,

$$ Q=It $$ $$\begin{align} Q & - \text{ charge, coulomb } (C) \\ I & - \text{ current, ampere } (a) \\ t & - \text{ time, seconds } (s)\\ \end{align}$$

Elementary Charge

Elementary charge is a fundamental physical quantity of electric charge carried by a single proton or electron. Usually denoted by \(e\) or \(q_e\) is equal to \(1.6 \times 10^{-19} C\).

If we want to calculate how many electrons is equivalent to 1 coulomb then,

$$ \begin{align} & \text{no. of electrons in one coulomb charge} \\ & = 1C \times \frac{1 electron}{1.6 \times 10^{-19} C} \\[2ex] & = \ 6.24 \times 10^{18} \ electrons \ \end{align} $$

Electric Current

Electric current is the flow of an electric charge. When there are a number of free electrons, they drift from one atom to another in a single direction when applied by an electromotive force. The unit is ampere named after Andre Marie Ampere (symbol: A) or Coulomb per second (symbol: C/s).