Basic Electrical Theory
METHODS OF PRODUCING VOLTAGE (ELECTRICITY)
The thermoelectric voltage in a thermocouple is dependent upon the heat energy applied to the
junction of the two dissimilar metals. Thermocouples are widely used to measure temperature
and as heat-sensing devices in automatic temperature controlled equipment.
Figure 15 Heat Energy Causes Copper to Give up
Electrons to Zinc
Thermocouple power capacities are very small compared to some other sources, but are
somewhat greater than those of crystals.
Generally speaking, a thermocouple can be subjected to higher temperatures than ordinary
mercury or alcohol thermometers.
Photoelectric Effect
Light is a form of energy and is considered by many scientists to consist of small particles of
energy called photons. When the photons in a light beam strike the surface of a material, they
release their energy and transfer it to the atomic electrons of the material. This energy transfer
may dislodge electrons from their orbits around the surface of the substance. Upon losing
electrons, the photosensitive (light sensitive) material becomes positively charged and an electric
force is created, as shown in Figure 16.
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