Learning about energy with experiments 1 – Making a light bulb

 

 

By Science Columnist Ho-Gwan Ko

 

 

American inventor Thomas Edison developed the incandescent light bulb, bringing light to the dark night. However, he was not the first person to invent the bulb. It has been known since the 18th century that a thin metal wire called a filament glows when heated by an electric current. However, it had not been widely used, because it broke too easily or became too hot.

Edison began his research in 1878 to make a practical incandescent light bulb. After trying to make filaments with various materials, he eventually invented the carbon incandescent bulb. Later, he also discovered that a filament made of burnt bamboo could burn longer, for more than 1,200 hours. In modern times, tungsten filaments, which are brighter and last longer, are used.

However, incandescent bulbs are less efficient. More than 90% of electrical energy is converted to heat, not light. Although they are for lighting, the efficiency is too low; for this reason, they are being used less all over the world. Korea stopped importing and producing incandescent bulbs in 2014. Nowadays, much more energy-efficient and bright LED lights are used.

However, the structure of an incandescent bulb is simple, making it a good tool to study its principle in experiments at home. When the current flows, the filament gets hot, because there is resistance that prevents electricity from going through it. Therefore, the temperature of the filament rises as the electrical energy turns into thermal energy, and the hot filament glows. Make an incandescent bulb to see how electrical energy turns into light and heat.

 

※ This experiment involves heat and smoke. Be sure to practice it with an adult.

 

What you need: a glass jar with a lid, 8 batteries (1.5V D-type), tinfoil, mechanical pencil lead, alligator clip wires, and tape.

 

 

1. Clip both ends of a piece of mechanical pencil lead with alligator clip wires. If the lead breaks easily, wrap both ends with tinfoil before clipping them. Place the lead on the lid of a glass jar.

 

 

2. Connect the batteries in series and tape them.

 

3. Put the glass jar upside-down over the lead and connect the other end of one wire to one pole of the batteries.

 

4. Connect the other end of the other wire to the other pole of the batteries.

 

5. Examine as the lead smokes and becomes red.