BuiltWithNOF
Electricity 4

What would happen if we tried to light up more than one bulb from the same battery?

This is an interesting question. If we could light up more than one bulb from the same battery then this would give us more light, but is it that simple?

Remember what we have found out so far........the old name for a light bulb was a ‘filament lamp’. The filament is a thin length of special wire which has been coiled up inside the bulb. It glows and produces light when an electric current flows through it.

Here we see some simple ‘series circuits’. The term ‘series’ is used to describe this simple way of connecting components together one after the other without any ‘branches’ which make the circuit more complex (see later).

We can investigate the original question by looking at the brightness of the bulbs in the circuits.

single bulb

one bulb on02

With one bulb and one battery the bulb is at full brightness.

two bulbs in series

two bulbs on

With two bulbs and one battery the bulbs are at medium brightness.

three bulbs in series

three bulbs on

With three bulbs and one battery the bulbs are dim.

Our conclusion is that...

In a simple series circuit we can light up more than one bulb from the same battery but the brightness of each bulb decreases.

We can explain this by thinking about the filament of wire inside the bulb and about the previous investigation involving the length of wire used in a circuit.

The longer the filament the more ‘resistance’ to the flow of current there is. Joining two bulbs together in a simple circuit is just like creating a longer filament so the current flowing is less and the bulbs will glow less brightly.

one bulb on arrow

The thick blue arrow represents lots of electricity flowing in the circuit and making the bulb glow brightly.

This is a LARGE CURRENT FLOW

three bulbs on arrow

The thin blue arrow represents a small amount of of electricity flowing in the circuit and making the bulbs glow only dimly.

This is a SMALL CURRENT FLOW

The next question could be....

Is there another way we can connect the same bulbs to a single battery and will this make any difference to the brightness of the bulbs?