A light bulb is a device that emits light when electric power passes through it. It is used in homes, cars and street lights. It has a glass mount with copper and lead wires that connect it to the electric circuit. The tungsten filament inside the bulb glows when electric current passes through it. The tungsten is coiled thin to prevent it from melting at high temperatures.
A tungsten filament is non-ohmic because it does not obey Ohm's law. Ohm's law states that current is proportional to voltage and inversely proportional to resistance. A resistor is ohmic if a graph of resistance versus voltage shows a straight line. A tungsten filament does not follow this rule because it changes its resistance as it heats up.
Non-ohmic materials are more prone to damage from sudden large amounts of current and cannot handle them. That is why they are more limited in their use than ohmic devices like diodes.
The first bulbs used carbon filaments until Joseph Swan and Thomas Edison developed a tungsten version in the 1800s. These were more durable and could be made to last longer. They started a revolution in home lighting, replacing oil lamps and kerosene lamps.
A diode is a semiconductor that has two terminals labeled as anode and cathode. It allows current to flow through it when it is forward biased (positively charged). When reversed (negatively charged), it blocks current and stops the flow of electrons. These specialized materials have many other uses and can be found in almost all electronic gadgets we use today.
