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Try this! A table-tennis ball which has been covered with a conducting paint is suspended by a silk thread so that it hangs between two metal plates. One plate is earthed. When the other plate is connected to a high voltage generator, the ball

A table-tennis ball which has been covered with a conducting paint is suspended by a silk thread so that it hangs between two metal plates. One plate is earthed. When the other plate is connected to a high voltage generator, the ball

  • Option 1)

    Is attracted to the high voltage plate and stays there

  • Option 2)

    Hangs without moving

  • Option 3)

    Swings backward and forward hitting each plate in turn

  • Option 4)

    None of these

 
Answers (1)
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As we learned

By electrostatic induction -

When charged body brought near an uncharged body, one side of neutral body becomes oppositely charged while other becomes same charged.

- wherein

 

 The table tennis ball when slightly displaced say towards the positive plate gets attracted towards the positive plate due to induced negative charge on its near surface.

The ball touches the positive plate and itself gets positively charged by the process of conduction from the plate connected to high voltage generator. On getting positively charged it is repelled by the positive plate and therefore the ball touches the other plate (earthed), which has negative charge due to induction. On touching this plate, the positive charge of the ball gets neutralized and in turn the ball shares negative charge of the earthed plate and is again repelled from this plate also, and this process is repeated again and again.

Here it should be understood that since the positive plate is connected to high voltage generator, its potential and hence its charge will always remain same, as soon as this plate gives some of its charge to ball, excess charge flows from generator to the plate, and an equal negative charge is always induced on the other plate.

 


Option 1)

Is attracted to the high voltage plate and stays there

Option 2)

Hangs without moving

Option 3)

Swings backward and forward hitting each plate in turn

Option 4)

None of these

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