Electric Current And Electric Circuits


An electric current is a flow of electric charge. In electric circuits this charge is often caused by moving electrons in a wire.

An electrical circuit is a path or line through which an electrical current flows. The path may be closed (joined at both ends), making it a loop. A closed circuit makes electrical current flow possible. It may also be an open circuit where the electron flow is cut short because the path is broken. An open circuit does not allow electrical current to flow. 

The SI unit for measuring an electric current is the ampere, which is the amount of flow of electric charge and is measured using a device called an ammeter.

The diagram below shows how a basic circuit looks like. 


Below is a basic set of symbols that you may find on circuit diagrams. 


It is very important to know the basic parts of a simple circuit and the symbols that relate to them. Please find them described below with their functions:

These are usually copper wires with no insulation. They make the path through which the electricity flows. One piece of the wire connects the current from the power source (cell) to the load. The other piece connects the load back to the power source.

The Load:
The load is a small light bulb or buzzer that lights when the circuit is turned on. The load is also known as a resistor.

The switch is simply a small gap in the conductor where you can close or open the circuit. When the switch is closed, the circuit is closed and electricity flows.
The power source is a cell.


Materials which do not allow electric current to pass through them are called insulators. Most of the non-metals are insulators, e.g. asbestos, rubber, wood, etc.