This should clear your understanding :)
A Torque is generated with combination of forces.In case of a DC motor these forces are generated by the interaction between the fixed field and rotating field.I know you will be clear with what is fixed field and rotating feild.If not feel free to ask.A very wrong notion that exists in every students mind is that, Back EMF is an evil force. It is not so back emf is used to control the speed (typical eg is trains! )
Back EMF is directly related with the EMF.The difference between the applied voltage and the back EMF is known as net voltage. Now with net voltage change the current in the motor changes.. Hence when the motor speed is zero,the back-EMF is zero.
(Had i known which year you are into i would have helped you in a much better way. If you are looking for more clarifications,mail it to me on namrata at crazyengineers.com)
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If A equals success, then the formula is: A = X + Y + Z, X is work, Y is play & Z is keep your mouth shut.- Albert Einstein 
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4th March 2007, 07:14 PM
Linear Mode
