Inside the glowing bulb
A thin wire called the filament gets hot and glows.
A lamp with a hidden wire
A torch lamp makes light. Look through its glass: you can see a thin wire held up by two thicker wires.
What do you think makes the light in this kind of lamp?
What this lesson covers
The idea
An incandescent lamp has a thin wire, the filament, supported by two thicker wires that form its two non-touching terminals (metal case and central tip); the filament gets hot and glows to produce light.
A lamp with a hidden wire
A torch lamp makes light. Look through its glass: you can see a thin wire held up by two thicker wires.
What do you think makes the light in this kind of lamp?
- The thin wire glows
- A tiny flame
- The glass glows by itself
Open the lamp
This lamp is drawn cut open. Find its parts. Then connect it to a cell and watch.
A hot thin wire
An incandescent lamp has a thin wire, the filament, supported by two thicker wires that form its two non-touching terminals (metal case and central tip). The filament gets hot and glows to produce light.
"Incandescent" means glowing because of heat. The two terminals are fixed so that they never touch each other.
- Part | What it does
- Filament | a thin wire inside the glass; it gets hot and glows
- Two thicker wires | hold the filament up
- Metal case | terminal 1 (one thick wire joins it)
- Metal tip | terminal 2 (the other thick wire joins it)
Notes
An incandescent lamp: a thin filament held by two thicker wires. Its two terminals are the metal case and the metal tip. They never touch. The filament gets hot and glows.
Check yourself
What is the thin wire inside an incandescent lamp called?
How many terminals does an incandescent lamp have?
Answer: 2
The lamp has two terminals: the metal case and the metal tip.
The two terminals of the lamp are fixed so that they...
How does an incandescent lamp give light?
- The terminal. Terminals are the metal case and the metal tip.
- The filament — correct. Yes! The filament gets hot and glows.
- The support. The thicker wires that hold it up are supports.
- touch each other. They are two separate terminals. They are kept apart.
- do not touch each other — correct. Yes! The case and the tip stay apart.
- turn into one wire. They stay two separate terminals.
- The filament gets hot and glows — correct. Yes! The hot thin wire gives the light.
- The glass bulb burns. The glass does not burn. It only holds the filament.
- The metal case glows. The case is only a terminal. The filament glows.