why negative sighn in faraday law of electromagnetic induction?

**waqarrashid33** · Nov14-09, 02:06 PM

plzzzzzzz any one can clear me on this point:
why -ve sighn comes in faraday law of electro magnetic induction?what is it sighnificance?if in answer value of induce EMF become -ve than waht will be its direction.

**Dadface** · Nov14-09, 02:33 PM

The minus sign expresses Lenz's law which in turn expresses the conservation of energy.........."the induced emf is in a direction such that it opposes the change producing it".As an example if you push a magnet towards a coil on closed circuit the induced current will cause the coil to become magnetised in a direction such that it repels the magnet.The work done in overcoming this repulsion is converted to electrical energy.

**waqarrashid33** · Nov14-09, 03:00 PM

if the -ve sighn is removed then what will be done with this law?

**Doc Al** · Nov14-09, 03:15 PM

Originally Posted by waqarrashid33

if the -ve sighn is removed then what will be done with this law?

What do you mean? You can't just "remove" the negative sign. As Dadface says, that negative sign in Faraday's law is called Lenz's law. Read about it here: Lenz's Law

**waqarrashid33** · Nov17-09, 06:53 AM

i mean that if we assume that lenz's law is wrong then what will happen?

**Doc Al** · Nov17-09, 07:21 AM

Originally Posted by waqarrashid33

i mean that if we assume that lenz's law is wrong then what will happen?

For one thing, energy will not be conserved--you'll have a source of "free" energy.

**Redbelly98** · Nov17-09, 08:54 AM

Originally Posted by waqarrashid33

i mean that if we assume that lenz's law is wrong then what will happen?

Then we get a contradiction between what the law says and what is actually observed.