Electricity is the flow of electric charge

Electric charges can flow in wires, light bulbs, and even in salt water.

In some ways, the flow of electric charges acts like the flow of water, so we will often make an analogy between electricity and water flow. Nonetheless, this is only an analogy. Electricity is obviously very different from water flow, as electricity can go through solid objects!

Let’s look inside a simple electrical appliance:

Wires, switches, and motors are connected in electric circuits.

A circuit provides a path through which electricity travels.

Electric circuits are similar to pipes for water

The difference? We can’t get electricity to leave the wire. If you cut a water pipe, the water comes out. If you cut a wire, the electricity immediately stops flowing.Electric current doesn’t flow except in complete circuits.

Switches turn circuits on and off.

Because a complete path through wire is needed, a switch works by breaking or completing the path.

Circuits are made of: wires, batteries, light bulbs, motors, switches, diodes, etc

To plan or explain a circuit, we use a circuit diagram.Symbols represent parts of the circuit. A circuit diagram is a shorthand method of describing a real circuit.

In many circuit diagrams any electrical device is shown as a resistor. A resistor is any component that uses energy, or anything that resists the flow of electric charge. We often draw things like light bulbs as resistors.

Real resistors look like this:

But they are drawn like this:

What flows inside a circuit? Electrical chargesIn an atom’s nucleus, we have protons (+) and neutrons (0). Outside the nucleus we have electrons (-)

The metal atoms in a wire do not move.

Nucleus doesn’t move Even the inner e- do not move.

Only the outermost e- (valence e- ) move

Electrons ( e- ) flow through conductors, but they normally cannot flow through the air.

If this wire is broken,then e- will not flow, and the bulb will go off.

(Obviously, in extreme circumstances e- can fly through the air, e.g. lightning.)