# Physics Class 12 NCERT Solutions: Chapter 1 Electric Charges and Fields Part 6

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Q: 21. A conducting sphere of radius has an unknown charge. If the electric field from the centre of the sphere is and points radially inward, what is the net charge on the sphere?

Answer:

Electric field intensity (E) at a distance (D) from the centre of a sphere containing net charge is given by the relation,

Where,

Permittivity of free space

And,

Therefore, the net charge on the sphere is

Q: 22. A uniformly charged conducting sphere of diameter has a surface charge density of . (A) Find the charge on the sphere. (B) What is the total electric flux leaving the surface of the sphere?

Answer:

(A) Diameter of the sphere,

Radius of the sphere,

Surface charge density,

Total charge on the surface of the sphere,

Therefore, the charge on the sphere is .

(B) Total electric flux leaving out the surface of a sphere containing net charge Q is given by the relation,

Where,

Therefore, the total electric flux leaving the surface of the sphere is

Q: 23. An infinite line charge produces a field of at a distance of. Calculate the linear charge density.

Answer:

Electric field produced by the infinite line charges at a distance having linear charge density is given by the relation,

Where,

Therefore, the linear charge density is .