Electrical circuits

In a nutshell

Electrical circuits are drawn using a pencil and ruler and using circuit symbols. There are two types of circuit, series and parallel. Current is the flow of electrical charge carriers, which are usually electrons.

Circuit symbols

Circuit symbols are simple ways to represent electrical components in a circuit. Electrical components are all of the equipment which make up the electrical circuit.

Make sure to learn the following circuit symbols.

Cell	Battery	Open switch
Closed switch	Lamp	Resistor
Variable resistor	Light dependent resistor	Diode
Light emitting diode	Ammeter	Voltmeter

Circuit diagrams

Circuit diagrams are always drawn using a pencil and a ruler. The circuit symbols above are used as the electrical components and straight horizontal and vertical lines are used to represent the wires which connect them.

When drawing circuit diagrams it is very important that the wires don't cross over each over.


A circuit containing a cell and a bulb	The circuit diagram of the electrical circuit

Types of circuit

Electrical components can be arranged in two different ways. Components are either in series or parallel. Series circuits are like a Netflix series, where the episodes are watched one after another. The same is true for a series type of circuit, the components are placed one after another.

The key detail to a series circuit is that there are no branches and the circuit diagram should look like a big loop. Branches is when the is more than one path electricity can take, the wire has a junction or a branch.

Parallel circuits contain branches which means that the wire splits into multiple paths for electricity to flow.

Some more complex circuits can be a mixture of both series and parallel.

Tip: A series circuit forms a big loop and a parallel circuit has branches.


A series circuit	A parallel circuit

Electrical current

If a circuit has been connected correctly, an electrical current will flow. An electrical current is the flow of charge around the circuit. In most electrical circuits the charge is carried around the circuit by electrons.

Curiosity: Electrical current is never used up in the circuit.

So, electrical current is the flow of charge.

A complete circuit

In order for the circuit to be complete, it must have a power source which will provide energy to the circuit and there must be no gaps in the wires or between the components.

If there are gaps in the circuit then the electrons can not move past the gaps, which means that current can not flow. If there is no power then the electrons will not get pushed around the circuit, which means there is no flow and hence no current.