Question

Five styrofoam balls are suspended from insulating threads. Several experiments are performed on the balls and the following observations are made –
(i) Ball A repels C and attracts B
(ii) Ball D attracts B and has no effect on E
(iii) A negatively charged rod attracts both A and E.
An electrically neutral styrofoam ball gets attracted if placed nearby a charged body due to induced charge. What are the charges, if any, on each ball?
A
+
+
+
-

B
-
-
-
+

C
+
+
+
-

D
0
+
0
0

E
+
0
0
0

Answer 1

Since the negatively charged rod attracts A and A replels C and attract B, so A is positive charged. Hence the charge on A is +ve.

Ball D attract B also ball A attract B, so B is negetive charged.

Ball A repels C so C is same charged as that of A and C is positive charged.

E has no charge on itself. So the charge is 0.

This is based on the fact that like charges repel each other and unlike charges attract each other. Also the balls which have no charge get attracted by any of the charge the positive or negative.