electric-charges-and-fields Question 21

Question: Q. 4. A charge +Q, is uniformly distributed within a sphere of radius R. Find the electric field, due to this charge distribution, at a distant point r from the centre of the sphere where :

(i) 0<r<R

(ii) r

A [Foreign, 2016]

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Solution:

Ans. We have

E=14πε0qr2, for a point charge 

Now (volume) charge density

ρ=Q(4π3R3)

(i) Charge contained within a sphere of radius r (0<r<R)

Q=ρ4π3r3=Q(r3R3)

Electric Field,

E=14πε0Qr2=(14πε0QR3r)1/2

(ii) For r>R

Electric field =( Electric field due to a point charge Q at the centre) 1

E=14πε0Qr2

[CBSE Marking Scheme, 2016]



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