Series Circuits
In series circuits, the current is the same at all
points. Using an ammeter to measure the current, if you set up a
circuit like the one above, all the ammeters would give the same
reading.
Bulbs resist the flow of current. The more bulbs you add to a
series circuit, the more resistance there will be. Less electric
current can flow if more bulbs are added. Less electric current
means that fewer electrons are passing a given point every
second.
Resistance reduces the amount of current flowing everywhere in
the circuit.
Parallel Circuits
In a parallel circuit, there are
junctions in the circuit so the current can flow around the circuit
in more than one way. In a series circuit the current decreases as
more bulbs are added. In a parallel circuit, as more bulbs are
added, the current increases. This is because bulbs added in
parallel offer less resistance.
Think of a water tank with a pipe to drain the water from the
bottom. If two pipes were added, twice as much water could drain
out. In a parallel circuit, the current is not the same at all
points. See the diagram above.
Electrical devices in our homes are connected in parallel so
that we can control each thing separately from the other. Christmas
lights are a classic example of a series arrangement. If one bulb
goes, none of the lights will work. House lights arranged in
parallel mean that each one can be turned on and off independently
of each other.
You can take one bulb out of a parallel circuit and the other
bulbs won't go out because the electricity can still flow round the
circuit.