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Faraday's ice pail experiment is a simple electrostatics experiment performed in 1843 by British scientist Michael Faraday [1] [2] that demonstrates the effect of electrostatic induction on a conducting container. For a container, Faraday used a metal pail made to hold ice, which gave the experiment its name. [3]
The original can be viewed here: Gold leaf electroscope diagram.jpg: . Modifications made by Krzysztof Zajączkowski (malyszkz) . I, the copyright holder of this work, hereby publish it under the following license:
The first electroscope was a pivoted needle (called the versorium), invented by British physician William Gilbert around 1600. [1] [2] The pith-ball electroscope and the gold-leaf electroscope are two classical types of electroscope [2] that are still used in physics education to demonstrate the principles of electrostatics.
Modern electrometers based on vacuum tube or solid-state technology can be used to make voltage and charge measurements with very low leakage currents, down to 1 femtoampere. A simpler but related instrument, the electroscope, works on similar principles but only indicates the relative magnitudes of voltages or charges.
English: Diagram of electric fields in Faraday's ice pail experiment.A charged object (small sphere) is placed inside a conductive metal shell (large sphere).The electrostatic field of the interior charge causes the mobile charges in the metal to separate, inducing a positive charge on the inner surface of the shell, and a negative charge on the outer surface.
Gold-leaf electroscope, showing induction (labelled polarity of charges), before the terminal is grounded. Using an electroscope to show electrostatic induction. The device has leaves/needle that become charged when introducing a charged rod to it. The leaves bend the leave/needle, and the stronger the static introduced, the more bending occurs.
This is part of the electrical induction process, and is an example of the related "Faraday's ice bucket". Also, the idea of bringing small amounts of charge into the center of a large metal object with a large net charge, as happens in Kelvin's water dropper, relies on the same physics as in the operation of a van de Graaff generator .
English: Diagram showing how a pith-ball electroscope works. The molecules (yellow ovals) that make up the pith ball (A) consist of positive charges (atomic nuclei) and negative charges (electrons) close together. Bringing a charged object (B) near the pith ball causes these charges to separate slightly.