Have you noticed that stuff sticks to your motor? If you drag your motor through a pile of paperclips, a few will get stuck to the side. What’s going on?
Inside your motor are permanent magnets (red and blue things in the photo) and an electromagnet (the copper thing wrapped around the middle). Normally, you’d hook up a battery to the two tabs (terminals) at the back of the motor, and your shaft would spin.
However, if you spin the motor shaft with your fingers, you’ll generate electricity at the terminals. But how is that possible? That’s what this experiment is all about.
[am4show have=’p8;p9;p21;p48;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials:
- 9-18V DC motor
- LED (bi-polar)
If you move a magnet along the length of a wire, it will create a very faint bit of electricity inside the wire. If you moved that magnet back and forth fast enough you could power a light bulb. However, by fast enough, I mean like 1000 times a second or more! If you had a stronger magnet, or many more coils in your wire, then you could make a greater amount of electricity each time you moved the magnet past the wire.
A motor has a coil of wire wrapped around a central axis, so instead of rubbing back and forth (which is tough to going fast enough, because you have to stop, reverse direction, and start moving again every so often), it rotates past a set of magnets continuously.
When you add a battery pack to the motor terminals at the back, you energize the coil inside the motor, and it begins to rotate to attempt to line up its north and south poles. But the magnets are lined up in a way that it will continually ‘miss’ and overshoot, which keeps the shaft spinning over and over, faster and faster.
You can turn your motor into a generator by simply giving the shaft a quick spin with your fingers. Remember that attached to this shaft is a coil of wire. When you spin the shaft, you’re also moving a coil of wire past the permanent magnets inside to motor, which will create electricity in your coil and out the terminals.
You can attach a low-voltage LED directly to the motor terminals and spin the shaft to see the LED light up. Depending on the size of the magnets inside your motor, you may need to spin the shaft super fast to see the LED light up. The larger the motor, the easier this activity is. Try using a larger, 12V DC motor from the main shopping list for this section.
[/am4show]
I think you’re asking, how does a motor generate electricity?
The electricity in your house actually runs forwards and backwards in an alternating cycle – it has no problems going one way or the other (unless you stick an electrical component like a diode in there to make it go only one way). You might want to look at the “Electricity Teleclass” so you can get a feel for how electricity works.
A motor generates electricity because it’s got magnets inside, and anytime you move a magnet past a coil of wire, you create an electric current inside the wire. How and why that is is explained in Unit 11 on Magnetism. Hope this helps!
how does the electricity go backwards?????
There’s a full lesson on them here:
https://www.sciencelearningspace2.com/unit-11-magnetism/lesson-2-electromagnetism/
with fun experiments you can do to really understand how they work! Let me know if you still have q’s after reading it over a bit… there’s a lot of pieces involved in understanding the whole picture or I’d normally just answer you with a sentence or two.
How do electromagnets work?
Caleb