Guidance for Enrolling in Low-Voltage Electrician Certification

(One)Electrical Basics：Direct Current Circuit I. Basic Concepts of the Circuit(1) Circuits and circuit diagrams，Circuits are pathways of electricity that connect electrical equipment and electronic components in a specific manner to meet certain needs. A circuit through which direct current flows is known as a DC circuit. Circuit diagrams are simplified drawings, using national standardized symbols, that are created for practical research and engineering needs to represent the composition and connection relationships of circuit devices and equipment.(Image 2-1). Circuits are generally composed of four basic components: a power source, a load, control equipment, and connecting wires.

Power Supply，This is a device that converts non-electrical energy into electrical energy and provides electrical energy to the outside, such as generators and batteries.

(2) Loads, also commonly referred to as appliances, are components or devices that convert electrical energy into other forms of energy, such as light bulbs, electric motors, and the like.

(3) Control devices are devices that alter circuit states or protect circuits from damage, such as switches, fuses, and the like.

(4) Wires, which are responsible for transmitting or distributing electrical power. In actual production, other equipment such as fuses and measuring instruments are often installed in the circuit for protection, measurement, and monitoring purposes. Figure 2-1 shows the simplest circuit. Circuits typically have three states: closed, open, and short-circuited. A closed circuit refers to a circuit that is continuously connected throughout, also known as a complete circuit, abbreviated as closed loop; normal working current is only present in a closed circuit. An open circuit is one where there is a break in the circuit, preventing the formation of a pathway; in this case, there is no current in the circuit. A short-circuited circuit is one where the current bypasses the load and directly conducts; when a short-circuit occurs, it often leads to equipment damage or fires due to excessive current, so short-circuiting is generally prohibited.

Section 2: Basic Physical Quantities in Electricity 1. Charge, Electric Field, and Electric Field Strength The fundamental particles that carry electric charge are known as charges. Particles that lose electrons and carry a positive charge are called positive charges, while particles that lose electrons and carry a negative charge are called negative charges. The quantity of charge is represented by electric charge or charge magnitude; the symbol for electric charge is Q, and its unit is C (Coulomb). An electric field is a special type of substance that exists in the space surrounding a charge and a changing magnetic field. The electric field exerts a force on the charge placed within it, which is known as the electric force; when a charge moves within an electric field, the electric force does work on the charge, indicating that the electric field possesses the characteristics of force and energy typically associated with ordinary matter. The strength of the electric field is represented by the electric field strength, symbolized by E, with units of V/m.

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