# Dynamo Mechanics

1. Nov 28, 2015

### WiseGreatTrixie

So..What would be the most efficient miniature dynamo system?

So my question to you, on the small scale, what would be the most efficient dynamo system? Small scale meaning a handheld size device. I know energy can be generated using Faraday's law, when you move a magnet near a coil it generates electricity. But how much, and which configuration would be optimum? Its been a while since I went to engineering school so I would like to learn a few things. Which is more important, should we focus on the Joules (weight energy) and physical force to turn a dynamo wheel, or is simply the moving of the magnet important, and the speed in which it moves? Is it better to turn a dynamo wheel using Joules, or is it better to have a moving magnet, light as a feather, exerting no force on the dynamo, and just magnetically generating electricity in the coils?

And, where would I get and purchase one of these devices, these dynamo devices?

For example, the system energy I wish to transfer into the dynamo, is 0.02 Joules.
The speed at which a magnet could move (in order to generate electricity) is .51 m/s.
How much energy could I get from this?

I would like a reference, specifically how much energy does it take to generate a electromagnetic field equivalent to the strength of a fridge magnet that lasts for 10 seconds?

2. Nov 29, 2015

### CWatters

I'm sure there must be papers on the efficiency of hand cranked generators. I didn't look hard but Google found one detailing tests of two slightly different hand cranked generators...

So it seems at least 50% efficiency is achievable.

That's not much energy. Is that all you have available or all you need to generate? 1 Watt is 1 Joule per second so this particular generator can deliver 8-10 Joules per second. More than 500 times what you need?

3. Nov 29, 2015

### WiseGreatTrixie

I would like to at least power a fridge magnet but I can't find any reference on google on how much energy that needs. (An electromagnetic equivalent.)

4. Nov 29, 2015

### CWatters

5. Nov 29, 2015

### WiseGreatTrixie

I thank you. However, I would like to know how much energy a fridge magnet has? Otherwise I will have to set up testing and test several paperclips to measure the max load of a fridge magnet vs. my custom magnet.

Last edited by a moderator: Nov 29, 2015
6. Nov 30, 2015

### CWatters

7. Nov 30, 2015

### Staff: Mentor

You are talking in the wrong units. A magnet does not store energy as a battery does. A magnet can exert a force. Force and energy are different things.

8. Dec 1, 2015