# Power Input for Motor and Back EMF

Hello everyone, I'm a bit confused about the power drawn by a motor. Since back emf reduces current when the motor is rotating at high speed, is it true that back emf reduces the power required at high speed? THX :D

NascentOxygen
Staff Emeritus
Hello everyone, I'm a bit confused about the power drawn by a motor. Since back emf reduces current when the motor is rotating at high speed, is it true that back emf reduces the power required at high speed? THX :D
Hi psycho. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

Yes. At the higher speed back emf is greater, so current reduces. Of course, you'll only see such high range speeds when the motor is unloaded, or very lightly loaded, so it isn't being required to produce much mechanical power (compared to its full capabilitiy) under those conditions, anyway.

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Hello nascent, how about the power drawn by the motor? Is it Also minimum at highspeed and maximum when stall?

NascentOxygen
Staff Emeritus