The gold-leaf electroscope

The gold-leaf electroscope

For the detection and testing of small electric charges, a gold-leaf electroscope is used. This instrument was invented towards the end of the eighteenth century by a Yorkshire clergyman named Abraham Bennet. Fig. 32.1 shows a common type of  electroscope. It consists of a brass rod surmounted by a brass disc or cap and having at its lower end a small rectangular brass plate with a leaf of thin gold or aluminium attached. The leaf is protected from draughts by enclosing it in an earthed metal case with glass windows. The brass rod is supported by passing it through a plug of some good insulating material such as alkathene at the top of the case

The gold-leaf electroscope
The gold-leaf electroscope

The three horizontal parallel lines shown at E in Fig. 32.1 is the conventional
symbol for an earth connection. The importance of having the case earthed will be understood after reading page 385

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