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My textbook (NCERT Physics Class 12th) has the following figure (Pg 212).

enter image description here

The Arm PQ is moved to the left side thus decreasing the area of the rectangular loop. This results in a decrease in magnetic flux in the Downward (inside the page) direction. Hence, according to lenz's law, the induced current should be in Clockwise direction but the book says the opposite.

Am I missing something? or is the book wrong?

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To me it seems that the book is indeed wrong. –  Joe Jan 31 '13 at 8:10
Yes, it's wrong. It's enough to see that the current pictured would induce a magnetic field directed outward, which would increase the variation of B in a positive feedback. Which is against the reason for which the "Lenz's minus" was introduced. –  Bzazz Jan 31 '13 at 10:55

2 Answers 2

I think the X's represent magnetic field going out of the page. If this is true, than the current will indeed be in the counter-clockwise direction, as the book says.

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No, X'es represent the field going inside the page. –  Aneesh Dogra Feb 3 '13 at 9:11

No the textbook is correct. Are you using Flemming's right hand rule?

Because according to the right hand rule if B (the magnetic field) is into the page and the motion of the wire is towards the left then the current will be pointing downwards. Relate that to part of the circuit parallel to the moving "arm PQ" and the circuit will be counter clockwise. :)

Here's an image of what the rule looks like: http://www.daido-electronics.co.jp/english/qa/magnet_lexicon/ha/images/ha13.gif

and I hoped this helped. Best of Luck, An IB Diploma Year II student

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