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Magnetism

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24 Dec 2007 13:20:53 IST

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a vertical wire carries a current in upward direction. An electron beam sent horizontally towards the wire will be deflected
(a)towards right
(b)towards left
(c)up
(d)down

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abhishek sinha

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24 Dec 2007 16:14:27 IST

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d) down ( since the electronic charge is negative & applying F = q ( v * B ) )

joy francis

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24 Dec 2007 17:01:42 IST

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Let the electron beam be projected from the left side of the wire towards the wire.

Direction of magnetic field due to the wire on the left side of the wire would be "out of plane"{since the current is flowing up} by right hand grip rule.

Force = q(vxb)

vxb is "downwards" , and since q is negative net force is upwards.

So , (c) option should be correct.

*note that if the electron beam is projected from the right side towards the wire , the ans would be same*

abhishek sinha

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24 Dec 2007 17:12:20 IST

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Basically the ans depends on the actual dirn . of velocity vector in the B plane( which is nothing but the horizontal plane ) .

Aatish Pandit

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24 Dec 2007 18:09:31 IST

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yes joyfrancis you are absolutely correct........

another approach can be that instead of taking the negative sign of charge into consideration at the end.......u could also have taken the direction of current to be just opposite to the flow of electrons....

I hope u understood what I meant to say.......

Krishna Gopal Singh

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24 Dec 2007 23:16:12 IST

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Yes it will be upwards only and logic of joy is correct. Well done

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