# Lorentz force opposing mechanical input to a generator?

When comparing between an electric motor, and a generator. I find them being quite similar. I can use and motor as a generator and vice versa.

What's confusing is the principle, the Lorentz force applied in the case of a motor, it causes the torque & acceleration of the armature. Simultaneously, causes the motional back-emf on the motor when it reaches high speeds.

What about the case of a generator? Certainly there is emf due to the Lorentz force, and when there is a load connected to a generator, current flows inside that magnetic field,is there a Lorentz force due to that generated current flow that opposes the applied mechanical input that induced the voltage of the generator?

• Of course. That's how the mechanical power is extracted. Nov 30, 2015 at 13:03
• Back EMF is always present, if BEMF is higher than applied voltage then its in a generator mode, otherwise its in motor mode. Both principles (motor and generator) are present all the time, the dominant one determines the mode of operation. Nov 30, 2015 at 14:18
• @BrianDrummond I don't understand, so there is a Lorentz force opposite to the direction of the mechanical input in every single generator? That's why when connected to a load, it's difficult to generate current? Nov 30, 2015 at 14:28