IIT JEE , AIEEE Forum - Physics , Electricity

sucess_seeker

A charge Q is uniformly distributed over a plasticplate. The electric field at a point P close to the center of the plate is 10 V/m. If the plastic plate is replaced by a copper plate of the same geometrical diumensions and carrying charde Q, the electric field at the point p will become 10 v because field does not depend on conducting material . Am i right?

ii) A metallic plate having no net charge is placed near a finite metal late carrying a positive charge. The electric force on the partice will be towards the plate. Why? it should be away from positive charge.

neeraj_agarwal_1990

see the neutral plate has no charge on it...

the attraction and repulsion is due to electrons...
when +ve plate is kept near it...the electrons come to the near surface(since it is metallic)...and +ve charge accumulates at the other end....so the force of repulsion b/w plate and +ve charge is less than the force of attraction b/w +ve plate and -ve charge because of lesser distance...
so there is a NET force of attraction...

neeraj_agarwal_1990

for the first one...
consider a closed gaussian surface which completely covers the plate....
when the plate is changed....the net charge remains same..the srea remains same....since every thing in gauss law remains same...so E should also remain same...

I think u are correct

edison

use the fact that near the plate it is like infinite charged plate and for non conducting charged plate the electric field is

E = sigma / 2 ebsylum

E = surface charge density / 2 (permittivity)

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