Science Buddies: "Ask an Expert"

This may seem stupid but it's something I've been wondering for a while. I have seen videos on YouTube of simple rotating electomagnets that use no power source producing energy to light a small LED but I've always wondered how much it is possible to produce with a more advanced electromagnet but it would have to be small no bigger than a tennis ball. And if you could produce an electromagnet this size is there anyway it could be used to produce enough electricity to power small home appliances like a hairdryer. Any replies would be great

Hi, two things:

1. Be careful with what you see in YouTube videos. There are a lot of hoax videos out there that may claim to get "free energy" from magnets somehow. The reality is that eventually friction will always slow the magnets down and bring them to a stop, and you need to spend energy in the first place to get the magnets spinning, so there is no "free" energy. This is, however, a great way to convert mechanical energy (the energy of something that's moving or raised off the ground) into electrical energy.

2. We have a project that explores exactly this topic: https://www.sciencebuddies.org/science- ... red-energy. This project lights up tiny LEDs like you saw on YouTube. The math behind how much voltage and current you will get is somewhat complicated, but you can read more about that at the links below. The short answer is that home appliances run off a very high voltage from wall outlets (120 volts) and draw a lot of current (at least a few amps). This amount of electricity is dangerous and can kill you - that's why it's not safe to stick your fingers in wall outlets. Tiny LEDs require MUCH less electricity (only a couple volts, and about 20 milliamps) so are relatively easy to power with household magnets and a coil you can make yourself, and it isn't dangerous to handle the coil.

https://en.wikipedia.org/wiki/Electromagnetic_induction

http://hyperphysics.phy-astr.gsu.edu/hb ... arlaw.html

Hope that helps. If you want to do a science project, the project I linked above will be a good starting point, but powering an appliance like a hair dryer is probably not a realistic (or safe) goal. You could go for something smaller like a flashlight that uses very bright LEDs.