When the pith balls are touching or when the electrons jump onto or off the neutral ball, the ball transfers small number of electrons with each swing and thus causing it to charge.
OK In Experiments Involving A Pith Ball Electroscope, What Cases The Pith Ball To Move?
A pith ball is suspended between a positively charged sphere B and earthed metal plate C. It is observed that the pith ball swings towards B,then to C and back to B again. After some time it stops. Why?