RGS Prelims 1991 P2 Q6
Two metal spheres X and Y on insulating stands are placed in contact and a positively charged sphere S on an insulating stand is brought near X and Y as shown in the figure below.
(a) Draw on the figure the charges, if any, on each of the spheres X and Y.
(Note: sketch it out, not draw on your monitor screen)
(b) If X is earthed without removing S, state the kind of charge, if any, on X and Y.
(c) If X is earthed in the presence of S, then having removed earth connection followed by the withdrawal of S, what will be the charge on X and Y if they are separated?
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Answer:
(a)
(b) If X is earthed,
X will be neutral; there's no charges on X. The electrons will flow down the path to earth.
Y will have positive charges.
(c) After removing the earth connection,
X and Y will be as shown. With the withdrawal of S, the positive charges in Y will distribute itself evenly between X and Y since they are in contact.
Thus, the charges on both X and Y will be positive if they are separated.
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