What is current？

We all touch and use electricity on a daily basis, but some basic knowledge about electricity may not be fully understood. This article will first introduce you to the basic concepts of electric current.

In electromagnetism, the amount of electricity passing through any cross section of a conductor per unit time is called current intensity, or current for short, and the unit is ampere (A). Current can be understood as the flow of electrons in a conductor. If you think of electricity as the flow of water in a river, then the current is the number of particles of electrons that gather and flow in one second. The size of the current is measured by the value of A. The larger the value of A, the greater the current passing through the circuit.

Current plays a vital role in the circuit, which is the basis of the work of electronic equipment. Whether it is household appliances, vehicles or communication equipment, are inseparable from the role of current. Therefore, understanding the basics of current is essential to understand how electronic devices and circuits work.

DC and AC

Current can be roughly divided into direct current and alternating current. Direct current, referred to as DC(Direct Current), refers to the unidirectional flow or movement of charge, usually electrons, and the direction of current and voltage is always the same.

Representative examples include dry batteries, batteries used for automobiles and the like, and lithium ion batteries. In direct current, the voltage is always positive (or always negative) and the current always flows in the same direction. Therefore, if the polarity is incorrect during installation, it may not work.

Alternating current is referred to as "AC(Alternating Current)", which refers to the direction and magnitude of current and voltage that change periodically over time. Its waveform is different, with sine wave, square wave, sawtooth wave and triangular wave shape.

The power frequency power supply represented by the household power socket generally uses alternating current. However, in the circuits of common electronic devices, alternating current is converted into direct current. So here's the question, "Why AC?"

The reason is the transmission of electricity. Due to the resistance of the wire, the current is prone to loss during transmission, but the loss can be reduced by increasing the voltage. However, because direct current is difficult to generate high voltage, it can only be transmitted in the form of alternating current, which is used as power frequency power supply to electrical equipment after step-down through transformer. The current is then usually converted to direct current in the circuit of the electrical device.