Why are light bulbs known as resistors?

Answer 1

The light bulb filament is made of a material fundamentally like the material used in resistors.

Answer 2

They both have a coil of wire in them that heats up. A light bulb make light with heat as a secondary effect while a resister generates heat and would make a small amount of light if exposed to air.

Answer 3

Most simple incandescent light bulbs are made of a thin section of tungsten through which the current flows.

This section of tungsten is called a "filament".

The tungsten filament has electrical resistance and so is a resistor.

As a resistor it develops a voltage drop. This voltage drop multiplied by the amperage passing through it equals the wattage of the bulb.

The heated tungsten gets to thousands of degrees above room temperature and becomes hot enough to produce yellow-white visible light.

As a resistor, the tungsten light bulb has a positive resistance coefficient.

This means that the electrical resistance goes up when the filament becomes hot.

For example, a 100 watt light bulb operated at 120 volts - it does not matter if it is AC or DC for this calculation - will have a resistance of 144 ohms when hot and draw 0.833 ampere.

When cold the filament typically has a resistance of only 10 ohms which increases as the filament heats up.

Comment

Light bulbs, or lamps, are not known as 'resistors'. They certainly have 'resistance', but they are not resistors. A resistor is an electrical component designed to provide a specific value of resistance into a circuit.