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# Daily Archives: December 20, 2011

## Electromagnetic Induction – Direction of Induced Current

I am unable to understand “How to find the direction of induced current?” please help me and explain me all the steps, how to do it? (Saroj Sharma asks)

Lenz’s Law states that the direction of induced current is such that it opposes the cause which produced it.

Illustration

If the south pole of  a magnet is brought near a coil, induced emf is induced in it. According to Lenz’s law, the induced current should oppose the south pole. Therefore the direction of induced current will be clockwise as seen from the magnet producing a south pole repelling the approaching magnet.

Fleming’s Right Hand Rule

Fleming’s Right Hand Rule states that if we stretch the Thumb, Forefinger and Central Finger of right hand in mutually perpendicular directions in such a way that Thumb shows the direction of motion of a  conductor, forefinger shows the direction of magnetic field, then the central finger shows the direction of induced current.

(While solving problems, please remember that the direction of current is opposite to the direction of flow of electrons, by convention)

## Light Year

A Light Year is the distance travelled by light in vacuum in one year. How many metres are there in one light year?  (Noor asked)

Speed of light in vacuum is 3 x 108 m/s

1 year = 365 days = 365 x 24 hours=365 x 24 x 60 minutes = 365 x 24 x 60 x 60 seconds

We know that distance = speed x time

Therefore,

1 LY = 3 x 108 x 365 x 24 x 60 x 60 m = 9.460528405×1015 m