Voltage is the amount of electrical potential energy between two points. It’s measured in Volts and represents the force that sends the electrons through a circuit’s conductive path and load.

We can think of voltage as “pressure”. This pressure comes from a power source (i.e. a battery) and pushes electrons through the conductive path. Voltage is measured across two points and will only cause electricity to flow if there is a conductive path between those 2 points.

Consider a water tank with a pipe attached below it where water can pass through it. We can use this analogy to represent voltage as the pressure of the water in the tank.

The greater the amount of water in the tank, the greater the pressure at the bottom of the tank.

Voltage analogy of a water tank that applies pressure to the bottom of the tank

Now imagine there was no pipe attached to the tank and the water has no place to go. There is still pressure at the bottom of the tank. This is the same in circuits. A battery on its own has a voltage, but electricity won’t flow until it is connected to a conductive path and a load.

Below is the schematic representation of a voltage source, usually representing a battery.

A schematic symbol of a battery consists of a group of alternating short and long horizontal lines.

In this lesson, we will work with voltage sources like the schematic above. They will have a positive terminal (the top vertical line) and a negative terminal (the bottom vertical line). When a voltage source is attached to a circuit it is a convention that electricity flows out of the positive terminal, through the conductive path and load, and back into the negative terminal.


Use the arrows to observe the effect of the water level on the pressure in the water tank.

Move to the next exercise when you are ready.

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