Introduction and Development of the Electroscope
– Early scientific instrument used to detect electric charge on a body
– Detects charge through movement of a test object
– Charge on an object is proportional to its voltage
– Requires high voltage sources such as static electricity and electrostatic machines
– Rough indication of charge; electrometer measures charge quantitatively
– First electroscope was the pivoted needle (versorium) invented by William Gilbert
– Pith-ball electroscope invented by John Canton in 1754
– Tiberius Cavallo made an electroscope with pith balls on silver wires
– Modern electroscopes use plastic balls
– Used in the discovery of cosmic rays by Victor Hess
Pith-ball Electroscope
– Stephen Gray used a hanging thread attracted to charged objects
– Consists of lightweight nonconductive balls suspended by silk or linen thread
– Induced polarization of atoms inside the pith ball causes attraction to charged objects
– Pith ball can be charged by touching it to a charged object
– Pair of suspended pith balls allows for polarity distinction and rough charge estimation
Gold-leaf Electroscope
– Developed by Abraham Bennet as a more sensitive instrument
– Consists of a vertical metal rod with two parallel strips of thin flexible gold leaf
– Gold leaves enclosed in a glass bottle with grounded metal plates or foil strips
– Spreads apart when terminal is touched with a charged object
– Leaves close together when terminal is grounded or through electrostatic induction
Charging and Discharging of the Electroscope
– Gold leaves spread apart due to charge conducted through the terminal and metal rod
– Grounding the terminal causes charge transfer and leaves to close together
– Electroscope can be charged without touching a charged object through electrostatic induction
– Same-sign charges repel each other, causing the leaves to spread apart
– Repelled charges can travel through grounding to leave the electroscope with opposite sign charge
Electrical Measurements and Radiation
– Electrostatic fieldmeter
– Faraday cup electrometer
– Measurement of electrical quantities
– Voltmeter
– Ammeter
– Electromagnetic radiation
– Ionizing radiation
– Non-ionizing radiation
– Radioactive decay
– Radiation detection
– Historical perspectives
– William Gilbert’s work on lodestone and magnetic bodies
– Contributions of Abraham Bennet
– Early understanding of electricity and magnetism
– Historical context of electricity and magnetism
Note: The references and external resources have been excluded from the groups as they do not directly fit into any specific concept category. Source: https://en.wikipedia.org/wiki/Electroscope
The electroscope is an early scientific instrument used to detect the presence of electric charge on a body. It detects charge by the movement of a test object due to the Coulomb electrostatic force on it. The amount of charge on an object is proportional to its voltage. The accumulation of enough charge to detect with an electroscope requires hundreds or thousands of volts, so electroscopes are used with high voltage sources such as static electricity and electrostatic machines. An electroscope can only give a rough indication of the quantity of charge; an instrument that measures electric charge quantitatively is called an electrometer.
The electroscope was the first electrical measuring instrument. The first electroscope was a pivoted needle (called the versorium), invented by British physician William Gilbert around 1600. The pith-ball electroscope and the gold-leaf electroscope are two classical types of electroscope that are still used in physics education to demonstrate the principles of electrostatics. A type of electroscope is also used in the quartz fiber radiation dosimeter. Electroscopes were used by the Austrian scientist Victor Hess in the discovery of cosmic rays.
