Final answer:
A short circuit occurs when there is an undesired low-resistance path across a voltage source. It can cause the device to stop working or overheat.
Step-by-step explanation:
A short circuit occurs when there is an undesired low-resistance path across a voltage source. The resistance of the short circuit is very small, causing a large amount of power to be dissipated in the short. This rapid dissipation of thermal power can lead to the melting or burning of surrounding materials.
In practical terms, when a device has a short circuit, it can cause the device to stop working if the power dissipation damages critical components. It can also lead to overheating if the thermal power generated is not adequately dissipated.