Asolid metal ball of radius 1.5 cm is located near a hollow plastic ball of radius 2 cm bearing a uniformly distributed charge of -9 nc on its outer surface. the distance between the centers of the balls is 7 cm. (a) click the edge of the metal ball that has an excess of positive charges. correct: your answer is correct. (b) what is the electric field at the center of the metal ball due just to the charges on its surface

Answer and Solution:

As per the question:

Uniform Charge distribution on the hollow sphere, q = - 9 nC =

Separation distance between the center of the two balls, d = 7 cm = 0.07 m

Radius of the metal ball, R = 1.5 cm = 0.015 m

Radius of the hollow ball, R' = 2 cm = 0.02 m

Now,

(a) The hollow ball has a uniformly distributed negative charge of - 9 nC so it will induce + 9 nC of charge on the solid ball near it.

The surface of the ball closer to the negatively charged hollow ball will get positive charge due to the force of attraction between the positive and negative charges and the negative charge of the metal ball are repelled to the farther surface of the ball.

(b) The electric field at the center of the metal ball is given by:

Since, the distance from the surface to the center of the metal ball is its radius.

where

k = electrostatic constant =

Thus

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