Does RPM affect electricity generation?

1. Mar 6, 2012

Ralphonsicus

Let's say I have a magnet inside a coil of wire. If I spin the magnet for a 10 second period, twice, the second time spinning it significantly faster, will more current be induced during the second period?

And would this apply to generators in wind turbines, etc.?

Thanks.

2. Mar 6, 2012

Hassan2

If you mean the induced "emf" is higher, you are right. According to Faraday's low, the induced emf is proportion to the rate of flux change. Higher speed, faster change of the flux. The current, however, depend on the load. If you have a resistive load and it is fixed, the current is proportional to the emf.

Yes this applies to wind generators too, but more wind power is required then and it may affect the efficiency of the win turbine.

3. Mar 9, 2012

cabraham

Yes and no. If the loading resistance is very large, then the induction exhibits "constant voltage" behavior. The induced emf varies with the speed/rpm. The current is the induced voltage divided by the loading resistance, again as long as Rload is relatively large. A large loading resistance results in a load current that is small, and consequently this small load current has a small magnetic field which is oriented with a polarity opposite that of the magnet. A small current and small magnetic field provides very little decrease in the overall magnetic flux.

But if the loading resistance is quite small, the induction exhibits "constant current behavior". In this instance, increasing speed has little effect on the induced current. I posted the equations for this type of problem recently. Maybe a search will turn it up. BR.

Claude