Question

A conducting sphere of radius 20 cm has
unknown charge. If the electric field at a
distance 40 cm from the centre of the sphere
is 1.2 × 10^3N /C and points radially inwards.
The net charge on the sphere is
a)-4.5× 10^-9C
b) 4.5 x 10^9C
0-5.3 x 10^-9C
d) 5.3 x 10^9C


plz give correct ans.
plz its very urgent
4​

Answer 1

Answer:

I think so that b

Explanation:

Answer 2

Given,

distance of electric field from the center of the sphere d = 0.4 m

Intensity of the electric field is E = $1.2*10^3 N/C$

To find,

Net charge(Q) on the sphere along with its direction.

now, intensity of electric field is given by

$E = \frac{Q}{4\pi \epsilon_o * d^2}$

we know that value of  $\frac{1}{4\pi \epsilon_o } = 9*10^9$. Thus, by substituting the values we get

$1.2*10^3 = \frac{(9*10^9)*(Q)}{0.4^2}$

∴net charge on the sphere is 'Q'

$Q = \frac{(1.2*10^3)(0.2^2)}{9*10^9} \\\\Q= 5.3 * 10^{-9} C$

NOTE: Here, the direction of the charge is also important. In the question it is mentioned that electric field points RAIDALLY INWARD.

∴ The net charge on the sphere is $Q = -5.33 * 10^{-9} C$

The correct option is 'c'

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