• Question: how do light bilbs work or whats in them to make them shine

    Asked by domo14 to Enda, Jean, Kate, Kev, Tim on 18 Nov 2012.
    • Photo: Tim Downing

      Tim Downing answered on 18 Nov 2012:

      Hi Domo14,

      Light bulbs work by sending energy in the form of an electrical current to the wire in the middle of the bulb. To release the energy from the current, the wire first heats, but then it becomes overloaded by the amount of energy coming in, and releases this as light energy. So although we associated light bulbs with the light they produce, most of the energy is released as heat – try touching one after turning it off!

      The difference between old traditional round light bulbs and the newer environmentally friendly ones is that the wire is self-replacing in the newer ones. In both types, inert gas inside the bulbs prevents the wire from burning out like a candle. But with newer ones any of the wire parts that evapourates due to the intense heat re-condenses back on the wire, meaning it lasts much longer.

      Tim

    • Photo: Jean Bourke

      Jean Bourke answered on 20 Nov 2012:

      Light is a form of energy. The electricity is the source of the energy and when it passes through the metal in the bulb the energy is released as light and heat.

      The more efficient a light bulb, the more electrical energy is converted in to light and the less is lost as heat. This is exactly the opposite of what you want your cooker to do!

      The colour of light from a hot object can be an indicator of its temperature, a the wire in a classic light bulb reaches temperatures of over 2500 degrees Celsius and fluorescent bulbs reaching over 5000 degrees Celsius!

      Remember heat and temperature are not the same thing: heat is a form of energy required to raise something’s temperature. Somethings need less energy to heat up than others so if you use a material that is easy to heat up, you waste less energy on heating and can make more light.

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