You can see two circuits here.
On the left you can see that the mills are placed next to each other. This is a series circuit. If you turn off the switch of a mill, you break the circuit. The electricity can no longer flow through it. No mill will turn.
On the right, the circuit branches into several paths, one through each mill. They then come together again. This is a parallel circuit. If you turn off the switch of a mill here, the electricity can no longer pass through it, but … it can still pass through via a roundabout route. The other mills are therefore still turning.
In a series circuit, the current (in amperes or A) through the three windmills is equal to the current supplied by the battery. The voltage (in volts or V) of the battery is distributed among the windmills. In a parallel circuit, it is the other way round. You can tell by the speed at which the windmills turn, and also by reading the meters.
Not sure what amperage and voltage are? We will explain below.
There is a battery in these circuits. This battery can also be compared to a vessel filled with water. There is a tap on that vessel, and the water in the vessel presses against the tap. If there is a lot of water in the vessel, it presses very hard. You can also compare this pressure with the electrical ‘voltage’ of a battery. The voltage is expressed in volts.
When you open the tap, the water flows. The flow of water can be compared with the electrical ‘current’. This is expressed in amperes. The electric current flows from one side of the battery, through a cable connecting the three mills, to the other side of the battery.
If the battery is empty, there is ‘no more water in the barrel’. There is no more voltage and therefore no current.
Series circuit in lawnmowers
To start the lawnmower, you have to press the start button and hold back the handlebar behind the wheel. If you don’t do one or the other, the lawnmower will stop working.
Both the start button and the handlebar are switches that are placed in series. This is for safety, so that your lawnmower doesn’t suddenly go all over the place when you let go.
Parallel circuit in modern Christmas lights
If one bulb in your Christmas lighting breaks down, the rest fortunately continue to work. This is because the bulbs are connected in parallel.
This was not the case with old Christmas lights. They were connected in series. If one bulb was broken, none of them worked.
