Basic Electrical Theory METHODS OF PRODUCING VOLTAGE (ELECTRICITY)The thermoelectric voltage in a thermocouple is dependent upon the heat energy applied to thejunction of the two dissimilar metals. Thermocouples are widely used to measure temperatureand as heat-sensing devices in automatic temperature controlled equipment.Figure 15 Heat Energy Causes Copper to Give upElectrons to ZincThermocouple power capacities are very small compared to some other sources, but aresomewhat greater than those of crystals.Generally speaking, a thermocouple can be subjected to higher temperatures than ordinarymercury or alcohol thermometers.PhotoelectricEffectLight is a form of energy and is considered by many scientists to consist of small particles ofenergy called photons. When the photons in a light beam strike the surface of a material, theyrelease their energy and transfer it to the atomic electrons of the material. This energy transfermay dislodge electrons from their orbits around the surface of the substance. Upon losingelectrons, the photosensitive (light sensitive) material becomes positively charged and an electricforce is created, as shown in Figure 16.Rev. 0 Page 23 ES-01
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