Wendy Klowaty, age 10, of South Burnaby, SC;;
What makes a light bulb burn out?
Almost every week, a lamp bulb somewhere in the house is almost sure to give up the ghost. Its radiant white light comes to a stop without so much as a flicker arid the useful life of that light bulb has come to an end. If you examine the burned‑out bulb, you may see smudges of dark soot on the inside of the glass which could have warned you that the bulb was, so to speak, on its last legs. More often than not, there are no warning signs at all. In the United States alone, some 700 million of these small tragedies happen every year.
The light which glows from a busy little electric light bulb is very hot. The heat and, of course, the light are made by the electric current in the circuit of copper wiring connecting the house to and from the generator, which may be many miles away. The light socket is a wayside station along the route of the electric current.. A light bulb has a metal foot which connects with the electrical current when we screw it into the socket. A system of wires, somewhat like an elaborate laundry line, connects the current from the metal foot in the socket up inside the glass bulb.
We can make or break the connection between the bulb and the current 3.n the wiring by turning the light switch on or off.. The current in the electric wire is the energy from countless trillions of tiny electrons. They are jostled by the far‑away generator and forced to move together in the same direction. When there are no wayside sockets turned on, this teeming energy stays inside the wires to and from the generator.
When we turn on the light switch, a small stream of electrons is forced to take a detour, They teem up the metal rods inside the light bulb and run right into a man‑made trap.
If you look inside the bulb, you will see that two sturdy upright poles are connected at the top by a fine coil of wire. This is the filament which finally ends the life of the light bulb.
In the wiring, the teeming electrons have plenty of room to move without becoming overheated. They also have plenty of room in the upright rods inside the light bulb, But suddenly they come to the fine filament and, like a river, they must squeeze through a narrow gorge, They crash and collide into each other and their speeding energy is turned into heat. The filament becomes so hot it glows and its glowing light brightens the room. All this heat, however, is bad for the metal of the filament. Bit by bit it evaporates and becomes weaken Finally it falls apart and the connection between the lamp and the electric current is broken. The bulb has burned out.
The first filaments were made of carbon which did not last very long. Science looked for a sturdier material which could stand. heat for a long time without breaking down. Our modern bulbs have filaments of tough tungsten or molybdenum. But even these tough metals break down and plunge us in darkness after so many hours of duty.