Motor run direction vs. polarity

Discussion in 'General Electronics Chat' started by samjesse, Mar 20, 2011.

  1. samjesse

    Thread Starter Senior Member

    Sep 14, 2008

    Given a DC motor, turn the shaft by hand in one direction, once would expct to see a voltage at its wiring terminals. Apply volt to the terminals, in the same polarity as above, would it turn the same direction as above or the opposite direction? if opposit, why?

  2. eblc1388

    AAC Fanatic!

    Nov 28, 2008
    It will turn in the same direction. Why? You would need to think in reverse.

    Think of a motor powered by a battery and is turning. You then remove the battery connection.

    Immediately after you have rmoved the connection, the motor is still turning because of inertia. Now this situation is no different than you are turning it by hand, albeit it rotates a lot faster and generates a much higher voltage at its terminals.

    We know that the motor terminal voltage must be the same as the battery when it is powered by the battery and rotating, thus if you rotates the motor by hand without the battery in the same direction, you will get the same voltage polarity.