# Homework Help: Simple electric motor

Tags:
1. Nov 15, 2014

### sharm8

1. The problem statement, all variables and given/known data
Hello ! I'm making a simple electric motor. Using copper wires and 1.5V battery.
2 magnets, 2 thumbtacks, 1 block of wood, 2 paper clips, and approximately 2m of insulated copper wire.
-The diameter of the loop must be 1"
CAN'T use other materials, only the above listed.

2. Relevant equations
I just want to ask what do I need to do to have 1500 RPM or more.. Thanks!
3. The attempt at a solution
-Maybe the setup/orientation will be a factor.
-See the uploaded file.

#### Attached Files:

• ###### Untitledk.png
File size:
11.8 KB
Views:
210
2. Nov 15, 2014

### Staff: Mentor

Hi sharm8, thank you for the diagram

3. Nov 15, 2014

### Staff: Mentor

For maximum speed I think you should aim to minaturize it, and make the rotating part as symmetrical and evenly balanced as you can. Use strong magnets, and a large sized battery. The big cells (D cells or bigger) are still only 1.5 volts but they can supply more current. If your copper wire is thin, perhaps run two strands together as one so it acts as though it is thicker copper.

You'll have no idea how fast it will spin, you just have to construct it using good techniques, then run it and see how it turns out.

Post a photo when you have it working.

Good luck!

4. Nov 15, 2014

### SteamKing

Staff Emeritus
A speed of 1500 RPM is pretty ambitious. You should set your sights on getting the motor to turn.
At a speed of 1500 RPM, a motor fabricated by hand is going to have a lot of imbalance in the rotor. Even if you were to achieve this speed, the motor would probably destroy itself due to vibration in short order.

5. Nov 15, 2014

### sharm8

Thanks for your advice, it will be a big help! :D
I think I will be using subwoofer magnet.
Thanks again, I will update you as soon as I finished it :D

Haha yeah you're right. But every 100 RPM, I will have 1 point. haha.. I guess there's no harm in trying..

6. Nov 16, 2014

### Staff: Mentor

Wear safety glasses when you're testing it it!

7. Nov 17, 2014

### CWatters

The strength of the magnets changes the efficiency of the motor (and that might be a factor here) but in general stronger magnets make the no load speed slower. The motor will accelerate from rest until the back emf equals the applied voltage. If you increase the strength of the magnets the back emf increases so it matches the applied voltage at a lower rpm. Best experiment with different magnets.

8. Nov 17, 2014

### sharm8

Noted :)

9. Nov 17, 2014

### sharm8

Nice idea. thanks :) I will have different magnets.

10. Nov 17, 2014

### dragoneyes001

the problem with 1500RPM is: with the limited materials you are allowed to use even if you use a near perfectly turned center piece to coil on you only have paper clips and thumbtacks to hold it in place while it spins neither of which will make a solid or even balanced axle.

11. Nov 17, 2014

### Staff: Mentor

Use 16d (16 penny) thumbtacks :D

12. Nov 17, 2014

### dragoneyes001

rebar sized paper clips?

13. Nov 17, 2014

### Staff: Mentor

There you go...

14. Nov 19, 2014

### CWatters

15. Nov 19, 2014

### dragoneyes001

I'd have to say 10k/rpm claimed is still a stretch but the idea of using the magnet to attach the screw to the battery was a nice touch removes half the instability of the shaft.

16. Jan 11, 2015

### sharm8

17. Jan 11, 2015

### Staff: Mentor

Well done!

Thanks for posting. http://imageshack.com/a/img29/6853/xn4n.gif [Broken]

Last edited by a moderator: May 7, 2017