DC Motor As Generator (4K)

Can DC motors be used as reasonably efficient DC generators? I do some (very) rough measurements on a DC motor to determine how efficient it would be as a generator.

https://www.youtube.com/watch?v=oRz0...ature=youtu.be

MATERIALS
- DC motor from a reverse osmosis water pump (32 v, 2 amp)
- DC power supply
- Volt and amp meters.


WARNING: Electricity always carries with it the risks of burns, fire, and electrocution. Motors can cause serious injuries. If you do not know, learn first or do not do it!