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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 charges
In 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.)