Basic Electronics - SPACE.RICE.EDU（基本的电子产品SPACE.RICE.EDU）.pdf

Basic Electronics Chapter 2, 3A (test T5, T6) Basic Electrical Principles and the Functions of Components Figures in this course book are reproduced with the permission of the American Radio Relay League. This booklet was compiled by John P. Cross AB5OX 26 PHYS 401 Physics of Ham Radio Basic Electrical Principles •  Conductors - keep loose grip on their electrons and allow electrons to move freely. Metals are usually good conductors. •  Insulators - keep close hold of their electrons and do not allow free movement of electrons. Glass, wood, plastic, mica, fiberglass and air are good insulators. •  Electromotive Force (EMF) is the force that moves electrons through conductors. Its unit of measure is the Volt. Think of it as similar to a pressure. •  Voltage Source - has two terminals (+ and -). Some examples are car batteries (12 volts DC), D cell batteries (1.5 volts DC) and a wall socket (120 volts AC). •  Current - is the flow of electrons. It is measured in amperes. (convention – current sign is – to electron velocity) •  Resistance (ohms, Ω) is the ability to oppose an electrical current. 27 PHYS 401 Physics of Ham Radio 28 PHYS 401 Physics of Ham Radio Circuit Definitions A circuit must close to be complete! 29 PHYS 401 Physics of Ham Radio Ohm’s Law •  Ohm’s Law relates Current (I), Voltage (E) and Resistance (R) •  The relationship can be written three ways: »  E = I x R