I think a basic starting point is power dissipation. Any electronic device, or circuit, has a power in and a power out. The power out may be electrical (power supply) or mechanical (motor) or other forms of energy (like your light bulb example). The light bulb is a tricky one since it is hard to measure the output in light and heat (IR). Other devices are easier, like a power supply. A supply might draw 1 amp at 120 volts, or 120 watts. The output is, as an example, 60 volts at 1 amp, or 60 watts. So the supply is dissipating 60 watts (of heat).
Power dissipation in electronic components, like diodes, transistors, resistors and even capacitors, is generally a calculable value. This dissipation is nearly always in the form of heat and must be taken into account in design, component selection and thermal design (heat sinking, air flow, etc).
Paul