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Electricity

Blazing goIITian

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19 Mar 2008 13:17:06 IST

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473

question for board xam

None

1.imagine that u are sitting in a chamber with ur back to one wall .an electron beam ,moving horizonatlly from back wall towards the front wall is deflected toward my right side by a strong magnetic field .what is the direction of magnetic field?please xplain im having doubt with the answer

2.if a bar magnet and the coil both are moved with equal velocity towards 1. each other and 2. away from each other .what will happen to the deflection of galvanometer coonnected with coil ?

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Comments (8)

arpan1

Blazing goIITian

Joined: 15 Mar 2008

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19 Mar 2008 13:23:10 IST

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second one seems easy

say the north pole of the bar magnet is moving towards the coil and the coil is also moving towards it...

as they approach each other, north pole is induced in the nearer end of the coil and they repel each other..

in this case, galvanometer shows deflection..

in the second case, magnet is at rest relative to the movindg coil...

hence no deflection...

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Sai Ganesh Bandiatmakur

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Joined: 17 Feb 2007

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19 Mar 2008 13:26:55 IST

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for the 1st one:
by fleming's left hand rule , current in dirn of back wall, force to the right, so field dirn shud be vertically down

debmalya choudhuri

Blazing goIITian

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19 Mar 2008 13:27:19 IST

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but what about the first one ? i know it is with left hand rule but the answer given in book is matching with mine please give an answer and an expalntion ?

arpan1

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19 Mar 2008 13:29:31 IST

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magnetic field is vertically up

(considering the fact that electrons are given)

Sai Ganesh Bandiatmakur

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19 Mar 2008 13:34:07 IST

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hey..sorry if my ans. is wrong..i think he considered sumthing like this:
a -ve charge deflected to right, so +ve charge deflected to left..and current in backward dirn, so again by FLHR, he got the dirn. of field vertically up? i am not sure abt this..was this the ans. given? but i still think B should be vertically down..

debmalya choudhuri

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19 Mar 2008 13:39:01 IST

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it is given upward the answer i am also having the same doubt as you the charge is negative then force on charge is towrads right the why to consider positive ?

arpan1

Blazing goIITian

Joined: 15 Mar 2008

Posts: 684

19 Mar 2008 13:40:43 IST

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vertcally upward is right. even i got the same...

see above

use F = q (v xB)
also remember that here u are considering electron

debmalya choudhuri

Blazing goIITian

Joined: 2 Jun 2007

Posts: 465

19 Mar 2008 13:43:43 IST

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yes yes got u

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