Friday, November 28, 2014

Powering a Lightbulb in the Microwave

We have really been enjoying learning about electricity with all our fun experiments and activities!  We have really been interested in electricity powering lights!  Although our LED play-doh doll house circuit was a great introduction to an electric light we wanted to understand how we got the light to glow.  We looked at this idea by investigating a light bulb and how energy is used to make light!

We started by looking at the anatomy of an incandescent lightbulb.  We have the metal at the bottom that connects to the circuit or wires that we get our electricity from.  The electricity then goes through a filament and this heats the filament up.  When the filament gets hot it will glow and that gives off light!

So we wanted to look at this a little bit closer.   We decided to see if we could heat up the light bulb another way.  {Warning - this experiment requires a lot of parental guidance}.  We took a 40W incandescent lightbulb and placed in a glass half filled with water (making sure the water covers the metal on the lightbulb).  Make sure to take out your turntable in your microwave and put your glass with lightbulb in the microwave for 45 seconds.

After a few seconds the lightbulb started to glow!   It started by flickering then it stayed on steadily and finally glowed!  What was fascinating was that it subtly changed colors a couple of times.  We thought this was pretty awesome!

After the 45 seconds we left it in the microwave for a bit to cool down as it was pretty hot.   We did not want to do it again until it was completely cool as we did not want to burst the bulb.

So why did the lightbulb glow - the same reason as when electricity goes through it!  The microwaves heated up the filament and when it got hot enough it started to glow!!   The water at the bottom covers the metal to keep it from sparking and getting too hot in the microwave.  We hope you will have fun with this lightbulb activity!



  • Incandescent lightbulb
  • Glass half filled with water
  • Microwave
  • Safety goggles if you have them!


  1. Place the lightbulb with the metal facing down in the glass of water.
  2. Remove the turntable from the microwave if you have one.
  3. Place the glass and lightbulb in the microwave and set the microwave for 45 seconds. ABSOLUTELY NO LONGER!
  4. Watch and see it glow!


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