explain the working and construction of electroscope

A simple electroscope consists of a glass jar resting on a wooden base. It is closed with an ebonite stopper having a hole. A brass rod passes through this hole. Two gold leaves are attached to the lower end of  the rod. A brass knob or disc is attached to the upper end of the rod. The glass vessels protects the gold leaves from air currents. Two strips of tin foils are fixed inside the bell jar facing the gold leaves. When the electroscope is in use, the metal foil is connected to the earth.

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hey annu u ac refer to this link:-

http://www.yourepeat.com/watch/?v=98A7INfsSxA&feature=youtube_gdata

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 its in your tb

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Constuction

Cut the stiff sheet of paper in a manner to fit the mouth of the bottle.Make a small hole in the stiff sheet and pass the copper wire through it such that there is no gap between the wire and the paper.Remove 2 cm of insulation from either end of the wire.Bend the lower end of the wire to form a hook. Cut 2 thin alluminium strips and hang them from the hook.Place the stiff paper carefully on the mouth of the bottle and seal it with a tape.Ensure that the strips of alluminium are intact when placed in the bottle.Electroscope is ready for use.

Working

When a negatively charged object is brought closer to electroscope it repels the electrons on the surface of the electroscope.The surface of the electroscope thus becomes positively charged.The electrons repelled from the surfacemove through the copper wire and move to the alluminium strips.Thus both the alluminium strips become negatively charged .As similar charges repel therefore the 2 strips move apart.Similarly when a positively charged object is brought closer to the electroscope, it will attract electrons from the electroscope.Thus electrons move from the alluminium foil towards the surface of the electroscope. The 2 alluminium strips thus get positively charged and again repel each other.Thus whenever a charged object is brought near to electroscope there is a repulsive movement between the alluminium strips.....

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An electroscope is a charge-detecting device which is based on the principle that objects charged at the same polarity will physically repel each other.With the help of this principle it is used to detect the presence and magnitude of electric charge. 

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