Electrical energy travels around a simple battery circuit from the battery to the device - a buzzer, bulb or motor. If the electrical energy in the circuit is too strong, it can damage the device. For example, a bulb may 'blow'. This means that the bulb will no longer work.
Simple circuits could look like this:
Bulbs may also glow very brightly because a lot of energy is being turned into light and heat.
If the electrical energy is not enough to power the device(s) in the circuit, we will also see the effects. For example, bulbs may be dim, or not produce any light at all.
The length of the wires in the circuit can also affect the brightness of the bulb. Very long wires make the bulb dim.