One of these is not the use of an electroscope

Analysis of the Question

The question asks us to identify which of the listed functions is not a use of a gold-leaf electroscope. To answer this, we need to understand what an electroscope is designed to do in a physics laboratory.

Concept Explanation

A gold-leaf electroscope is a sensitive instrument used primarily for detecting and analyzing electric charges. Its main functions include:

1. Detecting the presence of charge: It indicates whether an object is charged or neutral.
2. Testing the type of charge: By charging the electroscope first, we can determine if an unknown body has a positive or negative charge based on whether the leaves diverge further or collapse.
3. Comparing the magnitude of charges: The degree of divergence of the leaves gives an indication of the relative amount of charge.
4. Testing conductivity: It helps determine if a material is a conductor or an insulator.
5. Measuring ionization: It can be used to measure the ionization current in air, as ions in the air will cause a charged electroscope to discharge.

Step-by-Step Evaluation

• Option A (Testing the type of charge): This is a primary function of the electroscope. Correct.
• Option B (Measuring ionization current in air): This is a known application of the electroscope in experimental physics. Correct.
• Option C (Detecting the presence of charge): This is the most basic function of the electroscope. (Note: The question says "pressure of charge," which is a typographical error for "presence of charge"). Correct.
• Option D (Producing electric charge in a body): An electroscope is a detection device, not a generator. It cannot create or produce electric charge. To produce charge, you would need methods like friction (triboelectric effect), induction, or conduction from an existing source.

Conclusion

Since the electroscope is strictly a measuring and detecting instrument, it cannot be used to generate or produce electric charges. Therefore, option D is the correct answer as it describes a function the electroscope cannot perform.

Exam Tip: Whenever you see questions about laboratory instruments, always categorize them in your mind as either "Measuring/Detecting" or "Generating." Electroscopes, ammeters, and voltmeters are for detection/measurement, while Van de Graaff generators and Wimshurst machines are for producing charge.