Photoelectric Effect

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. Rev. 0 Page 23 ES-01