Question

For what purpose aluminium foil is stuck inside the electroscope

Answer 1

An Electroscope is an apparatus that is used to detect electrostatic field, it shows in a visible way the presence of an electric charge, with one you can even have a quantitative idea about how strong is the field. The simple electroscope proposed here is constructed with minimum and common materials and in fact you can build one right now in your kitchen. 

Answer 2

An Electroscope is an apparatus that is used to detect electrostatic field, it shows in a visible way the presence of an electric charge, purpose aluminium foil is stuck inside the electroscope

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