The example I am looking at in my text book starts by considering and area of the rotor surface of width w and length L.(adsbygoogle = window.adsbygoogle || []).push({});

Then the axial current flowing in the width w is equal to I=wA which is exposed to a radial flux density B

So from the Lorentz force F=IBxL the equation becomes

F= wABxL

so the force per unit area is F/wL which becomes:

F=BA

Then to obtain the torque the force per area is multiplied by the entire area of the rotor (2∏rL) then multplied by the radius of the rotor

So the overall torque equation becomes:

T=BA x 2∏rL x r

What doesn't make sense is how can the current be equal to wA? by the Lorentz equation the force on a current carrying conductor is IBxL so the width and area of the conductor carrying the current I does not matter? so why does it apply here?

Regards

Dan

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# Torque equation of an electric motor

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