Construção de um circuito fotoelétrico (fotoemissivo) com materiais acessíveis para utilização como recurso didático no ensino médio

The present work consists of constructing a photoelectric circuit using accessible materials and a multimeter capable of measuring electrical resistance in the range of 20 MΩ. This work is justified as it may encourage teachers to conduct a lesson that is not merely expository while addressing a topic in modern physics. Additionally, the experiment is simple and low-cost to construct, the materials are accessible, and the ultraviolet radiation from the lamp is of low intensity. First, a photoemissive cell was built using an aluminum plate, a stainless steel screen, and a nylon screen. Then, a circuit was assembled containing this cell and three NPN-type transistors. A 5 W ultraviolet lamp, commonly used in aquariums, was used to produce the photoelectric effect. The lamp was placed above the cell, and a multimeter set to the ohmmeter function was used to measure the photoelectric effect. Some difficulties encountered during the experiment are discussed to facilitate its application by teachers in classrooms or science laboratories, if the school have such a space. Finally, it can be said that this work demonstrates the feasibility of constructing an experiment to explore the photoelectric effect using low-cost and accessible materials. It can also be stated that the photoelectric effect is easily observed through the change in electrical resistance indicated on the multimeter. Therefore, teachers proposing to use such an experiment in class will face no difficulty in constructing or demonstrating the effect, with minimal risk due to the low intensity of ultraviolet radiation.