WAEC - Physics (1993 - No. 29)
Which of the following indicates the correct sequence of steps taken in charging a gold-leaf electroscope by induction? l. Removing the ebonite rod ll. Bringing a negatively charged ebonite rod close to the cap III. Earthing the cap IV. Disconnecting the earthing
III, II, I and IV
II, I, III and IV
III, IV II and I
II, III, IV and I
III, IV, I and II.
Explanation
Bringing a negatively charged ebonite rod close to the cap (II): This causes the electrons in the electroscope to be repelled, leaving the top of the electroscope positively charged. Earthing the cap (III): This allows electrons from the ground to flow into the electroscope, neutralizing the positive charge.
Disconnecting the earthing (IV): This isolates the electroscope while it retains the induced charge.
Removing the ebonite rod (I): This stops the influence of the charged rod. Therefore, the correct sequence is: II → III → IV → I.
Disconnecting the earthing (IV): This isolates the electroscope while it retains the induced charge.
Removing the ebonite rod (I): This stops the influence of the charged rod. Therefore, the correct sequence is: II → III → IV → I.
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