The correct option is (c) 2 and 3 only.
Explanation
A simple electroscope is a device used to detect the presence of electric charge on a body. It operates on the principles of electrical conduction and the electrostatic repulsion of like charges. The device typically consists of a vertical metal rod housed in a glass jar, with two thin metal leaves attached to the bottom end.
Statement-wise Analysis
- Statement 1 is Incorrect. An electroscope utilizes thin strips made of metal (commonly gold or aluminum foil), not plastic. Metal is a conductor, which allows electric charge to flow from the top of the device to the strips. Plastic is an insulator and would not facilitate the transfer of charge required for the device to function.
- Statement 2 is Correct. When a charged body touches the metal clip or knob at the top of the electroscope, the charge flows down the conductor to the foil strips. Since both strips acquire the same polarity of charge (either both positive or both negative), they repel each other and diverge (open up).
- Statement 3 is Correct. The working of the electroscope demonstrates that electrical charge can be transferred from a charged object to another body (the metal leaves) through a metal conductor. This process is known as charging by conduction.
Key Takeaway
The electroscope functions based on the principle that like charges repel. It requires a continuous conducting path (metal rod and leaves) to transfer charge from the source to the detector leaves, causing them to diverge.