As, electrons are negatively charged, it can be further added that electric current is the flow of negative charge.
In order for an electric current to flow there needs to be complete circuit with no gaps. A basic electric circuit consists of a metallic wire connected to an electrical cell and an electrical component such as a lamp. The metallic wire contains a large number of free electrons that can move easily from atom to atom, it is the movement of these free electrons that give rise to the current.
When the switch is in the “off” position there is a gap in the circuit and the electrical current cannot flow. In the “on” position the switch completes the circuit allowing current to flow and thereby lighting the lamp.
1 ampere is a set number of electrons flowing through each point of an electrical circuit per second. 1 ampere is approximately 6 million million million (6 x 1018) electrons per second flowing past each point. As the charge on electrons is tiny the unit of charge used is the coulomb (C). 1 coulomb is equal to the charge on 6 million million million (6 x 1018) electrons. Therefore when a current in a circuit is 1 ampere the flow of charge is 1 coulomb per second.
By connecting an ammeter in series in an electrical circuit the size of the electrical current can be measured.
It is important to remember that as an electrical current flows through a component such as a lamp or ammeter it is not used up but flows in a continuous loop. The battery supplies the energy source for the electrons to move. These transfer or loose energy when passing through components such as lamps in the form of heat and light but do not get used up themselves. Therefore in series circuit the electrical current is the same in all parts of the circuit.