Why is an incandescent bulb hot to touch when it has been switched on for a while?
The incandescent bulb heats the filament (typically a coil of wire) to thousands of degrees so that it glows.
Since the bulb itself is generally at most a few inches from the filament, it gets pretty hot as well.
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An incandescent bulb becomes hot to touch when it has been switched on for a while due to the process of converting electrical energy into light and heat. To understand this better, let me explain the working principle of an incandescent bulb.
Inside an incandescent bulb, there is a thin filament made of tungsten. When electricity flows through this filament, it encounters resistance, causing the filament to heat up. As the temperature rises, the filament starts to glow and emits light.
However, not all the electrical energy is converted into light. In fact, a significant amount is converted into heat due to the resistance of the filament. This heat is extremely high, reaching temperatures well over 2000 degrees Celsius (3600 degrees Fahrenheit).
Since an incandescent bulb is generally made of glass, it acts as an insulator, preventing the heat from escaping easily. As a result, the heat accumulates within the bulb, causing it to become hot to touch.
It is worth mentioning that incandescent bulbs are not very energy-efficient, as most of the electrical energy is wasted as heat rather than producing light. This inefficiency led to the phasing out of incandescent bulbs in many countries, in favor of more energy-efficient alternatives like LED bulbs.