Electric components generate heat due to the Joule heating (also known as ohmic heating or resistive heating). Joule's law predicts that if current flows through a component with some electrical resistance, the electrons will transform part of their kinetic energy into heat (due to the collisions with the particles that form the conductor component).

The amount of heat generated can be quantified as:

$$P = V \cdot I = I^2 \cdot R$$