We will be using batteries for all the projects, so let’s start by trying to understand the principle behind batteries and circuits in general.
Consider two water tanks as shown – tank B is at ground level, while tank A is at some height. Due to this height difference, the water in tank A is said to have higher potential energy compared to that in tank B. If we were to connect the two tanks together, it would result in water from tank A flowing into tank B.
This is similar to what happens in a circuit. The two tanks form the battery, with the positive terminal being tank A, while the negative being tank B. The pipe is similar to a circuit which results in electric current flowing through it.
The diameter of the pipe determines the rate at which water can flow through it, while the resistance of the circuit, determines the current that can flow through the circuit. We will look at resistors in the next post.
The rate at which water can flow also depends on the amount of water. If we have a lot of water in tank A, it will cause water to flow at a maximum rate because of the high potential difference. Batteries also have something called potential difference and this also controls the amount of electric current flowing through the circuit. The potential difference is called voltage and is generally indicated on the batteries. The AA batteries have a potential difference of 1.5V, whereas the bigger battery has a potential difference of 9V between the terminals.
One more thing to mention is that batteries can be connected together to increase the potential difference. So if we take 2 AA batteries and connect them as shown above, the potential difference at the ends will be 3V – that’s 1.5v + 1.5V. We can also turn the batteries around and connect the terminals together which is the same as what we did before.
That is what exactly happens in the battery box. The two batteries are connected internally giving us the two wires. The battery box also contains a switch so instead of the red wire being directly connected to the positive terminal, it is connected through a switch. When we slide the switch to the ON position it connects the red wire to the positive terminal like so.
I hope this gives you a rough idea about batteries and battery boxes. We will start building circuits in the next post.