# Q 1.21: A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is  and points radially inward, what is the net charge on the sphere?

We know, for determining the electric field at r>R for a conducting sphere, the sphere can be considered as a point charge located at its centre.

Also, electric field intensity at a point P, located at a distance r, due to net charge q is given by,

Given, r = 20 cm = 0.2 m  (From the centre, not from the surface!)

Therefore, Charge on the conducting sphere is  (Since flux is inwards)

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