What have we found out?
With the wire at its longest the bulb is off! Or is it?????
With the wire at its shortest the bulb is brightest.
As the length of wire increases the bulb gets dimmer.
As the length of wire decreases the bulb gets brighter.
There may be a point where the wire is so long that the bulb is too dim to see! But, if we make the room darker we may still be able to see a glow from the bulb. This teaches us that ‘how’ we observe things is very important.
We can conclude that:
The longer the wire the smaller the flow of electricity and the smaller the flow of electricity the dimmer the bulb glows.
When the wire is very long there is so small a flow of electricity that we can’t see the bulb light up at all but there is still electricity flowing!
We can prove this in an interesting way by connecting a buzzer into our circuit when the wire is at its longest. The buzzer still buzzes even though the bulb is not lit! This is because a buzzer only needs a very tiny flow of electricity to make it work.
Bulbs need a minimum amount of electricity in order to make them light up and different bulbs have different needs. A car headlight requires lots of electricity and would not light up at all using one of our small batteries. It needs a very powerful, and large, car battery to provide the large flow of electricity.
A flow of electricity is called a ‘current’ so we can use the terms low current and high current to describe the amount of electricity flowing through a wire.
We have used the brightness of a bulb to investigate the amount of electricity flowing in a wire. Can you think of how other components might be affected by changing the flow of current?