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I have already been searching for this but couldn't find something reasonable

I want to know that when will be the value of back emf maximum in a dc motor? At no load or full load or half load?

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  • \$\begingroup\$ Actually back EMF is maximum at negative load ... when something is pulling the motor round faster than its no-load speed. But then it's just called "emf" and the motor isn't a motor any more - it's a generator. \$\endgroup\$ Nov 23 '19 at 13:57
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The back EMF is proportional to speed. As the load increases, the speed will decrease. That will cause the back EMF to decrease. Note that there is a voltage drop across the armature resistance. That voltage drop plus the back EMF is equal to the supply voltage.

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  • \$\begingroup\$ You mean no load is answer? \$\endgroup\$
    – Man
    Nov 23 '19 at 17:46
  • \$\begingroup\$ Yes, I mean no-load is the answer. \$\endgroup\$ Nov 23 '19 at 17:50

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