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Chapter 5 Ionizing Radiation: Dose and Exposure—Measurements, Standards and Protection
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
Becquerel used another form of interaction between ionizing radiation and matter to detect the radiation emitted by the uranium salt. He used a gold leaf electroscope (see figure 5.6), which measures the electric charge placed upon it. If there is an excess of electrons on the electroscope then the negatively charged electrons will repel each other and so the gold leaf will be repelled by the static metal plate. If the electrons can escape from the electroscope then they will do so, but they cannot pass through the surrounding air. However, Becquerel found that, if the uranium salt was left close to the electroscope, the gold leaf fell and the electrons were apparently escaping. He explained this by saying that the ionizing radiation from the uranium was able to remove electrons from the atoms in the air surrounding the gold leaf; so ionizing the air. Electrons from the gold leaf could then be attracted by, and combine with, the positive air ions, thereby escaping from the electroscope. The negative air ions would be repelled by the gold leaf.
Testing of Semiconductor Scaled Devices
Published in Balwinder Raj, Ashish Raman, Nanoscale Semiconductors, 2023
One of the earliest detectors was the electroscope. The electroscope used two gold leaves that repel each other when they are charged (because of the ionization occurring due to radiation). Thus, the sensitivity can be measured at a better level. Researchers could also measure beta- or alpha-particles. The understanding of basic principles of radiation could be developed by these early devices, for example, cloud chambers.
Direct Current (dc) Electronics
Published in Dale R. Patrick, Stephen W. Fardo, Electricity and Electronics Fundamentals, 2020
Dale R. Patrick, Stephen W. Fardo
Electrical charges are used to filter dust and soot in devices called electrostatic filters. Electrostatic precipitators are used in power plants to filter the exhaust gas that goes into the air. Static electricity is also used in the manufacture of sandpaper and in the spray painting of automobiles. A device called an electroscope is used to detect a negative or positive charge.
Robert Hare's Theory of Galvanism: A Study of Heat and Electricity in Early Nineteenth-Century American Chemistry
Published in Ambix, 2018
Hare also supported a chemical theory of the pile. However, in contrast to Davy’s, Cruickshank’s, and Wollaston’s views, he wrote: “I have for some time been of opinion that the principle extricated by the Voltaic pile is a compound of caloric and electricity, both being original and collateral products of Galvanic action.”42 Early experiments with the pile demonstrated that, in addition to producing electricity, it also generated a great deal of heat. Davy, for example, measured an increase in ambient temperature during the electrical decomposition of salt water.43 He also observed that passing large quantities of the pile’s electricity through thin wires set them on fire, and when he ignited current-carrying wires in a vacuum, the wires burned for a prolonged period of time. Moreover, heating could also generate electricity. Davy observed that “[i]f, for instance, a plate of metal, strongly heated, be placed upon an electrometer [a gold-leaf electroscope] and a drop of water be poured upon the plate, at the moment the water rises in vapour, the gold leaves of the electrometer diverge with negative electricity.”44 Repeating this experiment with a variety of different substances, he concluded that “ … when vapour is formed or condensed, the bodies in contact with the vapour, become electrical.”45 Whereas Davy suggested that these experiments challenged the notion that there existed a material form of heat, Hare asked: what role did caloric play in these experiments?46