In a circuit where there is change in a magnetic flux, Back EMF is induced.

When back EMF is increases it reduces the source EMF( or oppose it) and therefore, the current is reduced, in order to stabilize current as it was before back EMF was created to reduce current, what can be done?

Note: Power can be changed. So what might be the solution? Increase the resistance so that source EMF would be higher than the back EMF, therefore... stabilizing current at the cost for higher power?

  • \$\begingroup\$ I can't make sense of this gibberish. \$\endgroup\$ – Olin Lathrop Jun 14 '14 at 23:37
  • \$\begingroup\$ @OlinLathrop Wow, note to self, never write something when you're extremely tired. Sorry there, I corrected the question now. \$\endgroup\$ – Pupil Jun 15 '14 at 0:07

When back EMF (such as from a motor) increases it doesn't reduce the source EMF (because that is a voltage source and is fixed by the power supply generating it). What the back emf does is act in opposition to the source voltage so that if back emf increases the current taken by the (say) motor decreases.

Typically a motor with no mechanical load will produce a high back emf and this keeps the motor current small - this is logical because on no-load the motor current should be small. As the mechanical load on the motor increases, the back emf decreases and more current is taken.

I'm trying to tease a question from the words and misinformation posted and hopefully I've answered the correct question.

  • \$\begingroup\$ Okay, can we increase source EMF so that it acts against the back EMF as it increases, so that current is not changed and stays the same? \$\endgroup\$ – Pupil Jun 14 '14 at 19:55
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    \$\begingroup\$ @Key - it's called a constant current generator and is an op-amp, a transistor and a resistor - it raises the source voltage to keep the current constant. \$\endgroup\$ – Andy aka Jun 14 '14 at 20:38
  • \$\begingroup\$ Just wanted to know if the principle will allow such an idea... \$\endgroup\$ – Pupil Jun 14 '14 at 21:17
  • \$\begingroup\$ If it's to do with DC motor speed and torque control then this is commonly done. \$\endgroup\$ – Andy aka Jun 14 '14 at 21:49
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    \$\begingroup\$ I think this idea could work but is sufficiently evolved from the original as to warrant another question. More people are going to contribute too hopefully. You can mark this question as answered if you think it is. \$\endgroup\$ – Andy aka Oct 20 '14 at 15:06

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