a. Hang the polystyrene ball coated with aluminium using dry silk thread.
b. Charge the glass rod and bring it close to but not touching the suspended ball
c. Touch the side of the ball away from the glass with a finger.
d. While holding the glass rod, withdraw the finger and then the glass rod.
e. Bring the charged polythene rod (negatively charged) close to but not touching the polystyrene ball.
Nb. When a charged polystyrene rod is moved close to the charged ball they repel, hence the polystyrene got the opposite charge of the charging rod.
joseph rimiru answered the question on November 1, 2017 at 20:06
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