The full name of alternating current is alternating current, which means that the current direction changes periodically at any time, and the running average value in a period is zero.
The full name of DC·DC is direct current, also known as "constant current". Constant current is a kind of DC, and its size and direction remain unchanged. To transmit the same power, the conductor used in DC transmission is only 2/3 ~ 1/2 of that of AC transmission.
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nature
According to the principle of Fourier series, periodic function can be expanded into infinite series composed of sine function and cosine function, and any non-harmonic alternating current can also be decomposed into a series of harmonic sine and cosine alternating current. ?
frequency
The frequency of alternating current refers to the number of periodic changes in unit time, in hertz, which is reciprocal to the period. The frequency of alternating current in daily life is generally 50 Hz or 60 Hz, while the frequency of alternating current involved in radio technology is generally large, reaching the measurement of kilohertz (KHz) or even megahertz (MHz).
The AC frequency of power systems in different countries is different, usually 50 Hz or 60 Hz. Countries and regions in Asia that use 50 Hz mainly include China, Japan, Thailand, India and Singapore, South Korea, the Philippines and Taiwan Province Province of China use 60 Hz, most countries in Europe use 50 Hz, and countries in America use 60 Hz mainly include Mexico, the United States and Canada.