IIT JEE , AIEEE Forum - Physics , Electricity - 486 veiws no answer-electrostats reason assertion

ankur.kkhurana

ASSERTION
a charge q is placsed inside a metallic shell .P is a point inside metallic shell.Electric feild at point P is zero

this is a correction i am doing now if anyone who hadn't understand the problem.point P reside in conductor metallic shell not in cavity

REASON
net electric field in a conductor under electrostatic condition is zero.

Ans give is d
i am getting A

ASSERTION
Electric current will not flow between two charged bodies when connected if their charges are same

REASON
current is rate of flow of charges

what is ans of this

utkarshsinha

The second one..

Assertion is wrong, Reason should be.. "Current is the rate of flow of charge"...

Charge flows when there is potential difference, the amount of charge does not matter.

ankur.kkhurana

ans given is d
but i say it shld be e as charge flow from high potential to low potential
and here in conductor after attaching them they becum eqipotential
so my reason is justified

amangem

arrey yaar if the bodies carry equal charges they are already at the same potential ... so no redistribution of charge will take place..

and in the first case ... the first statement is wrong.... draw the diagram and chek... and as far as the correctness of the situation is concerned ... see net field inside a condustor is 0 as tthere is no charge inside the conductor in electrostatic situation ..
but in the first case ... there IS charge inside the conductor .... it is place and can not move to the surface ... so first statement is wrong...

ankur.kkhurana

but it is a shell

adarshstays

ref to the second one:
rem current flows only if the circuit is complete..
when u bring two charged spheres near , the circuit is not fully made,.
& if u bring them together, there might be flow of charges from one sphere to another... this ends up in an equipotential surface..

ankur.kkhurana

that is not necessary.Charges flows from high to low potential

amangem

yeah it is a shell ....
so the fact is that charge can not physically redistribute ... it can only induce a charge on the shell...
so if u draw a gaussian surface thru p , there will be a charge enclosed inside the surface .... so there will be some el fielld thru the gaussian surface and hence at p ...
i hope u got my point
cheers

thevyzz

for the seconf one,

electric current will not flow only when the potentials are same, so the assertion is wrong

and the reasoning statement " current isthe rate of flow of charges" is absolutely correct ( you made a typo there).

so answer is definitely d

same way,

when there is a charge q at the centre of the sphere, the E at the metallic shell will not be zero

E = -dv/dx and potential changes here wrt to distance

and the reasoning statement is once again a fact, so answer is d

ankur.kkhurana

but after apllying gauss law we found that e.dx = 0, so net charge is 0 that can be justified by fact that - q charge is in induced form in inner shell.
@ ammangam
charge in metal rest on surface
will u plz explain it again i can't understand ur explaination

amangem

yes ... charge in a metal rests on a surface ... but see a shell is hollow ... so how can the charge move to the outer portion... it is a shell ... not a sphere ... had it been a sphere u wud have been correct ... u still are but are confusig urself ....luk at the subtle difference..ok

utkarshsinha

ankur.kkhurana

experts plzz see here .

magiclko

first question

thr is charge inside the shell, this will induce charge on the surface of the shell... using gauss law, thr will be some electric field!!!

I can be wrong, cuz m nt that gud at phy.. but this is what i have studied...

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