Search results
Results From The WOW.Com Content Network
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.
Such experiments led to the theory of two types of electric charge, one being the negative of the other, with a simple sum respecting signs giving the total charge. The electrostatic attraction of the charged plastic pen to neutral uncharged pieces of paper (for example) is due to induced dipoles [ 36 ] : Chapter 27 in the paper.
But when the inducing charge is moved away, the charge is released and spreads throughout the electroscope terminal to the leaves, so the gold leaves move apart again. The sign of the charge left on the electroscope after grounding is always opposite in sign to the external inducing charge. [5] The two rules of induction are: [5] [6]
The charge due to polarization is known as bound charge, while the charge on an object produced by electrons gained or lost from outside the object is called free charge. The motion of electrons in conductive metals in a specific direction is known as electric current.
The experiment shows that an electric charge enclosed inside a conducting shell induces an equal charge on the shell, and that in an electrically conducting body, the charge resides entirely on the surface. [4] [5] It also demonstrates the principles behind electromagnetic shielding such as employed in the Faraday cage.
The initial motivation for the development of the Van de Graaff generator was as a source of high voltage to accelerate particles for nuclear physics experiments. [1] The high potential difference between the surface of the terminal and ground results in a corresponding electric field .
Electrostatic machines are typically used in science classrooms to safely demonstrate electrical forces and high voltage phenomena. The elevated potential differences achieved have been also used for a variety of practical applications, such as operating X-ray tubes, particle accelerators, spectroscopy, medical applications, sterilization of food, and nuclear physics experiments.
Among other applications, electrometers are used in nuclear physics experiments as they are able to measure the tiny charges left in matter by the passage of ionizing radiation. The most common use for modern electrometers is the measurement of radiation with ionization chambers, in instruments such as geiger counters .