Introduction to voltage:

Also known as potential difference or potential difference, it is a physical quantity to measure the energy difference of unit charge in electrostatic field due to different potentials. The magnitude of voltage from one point to another is equal to the work done by unit positive charge moving from one point to another due to electric field force, and the direction of voltage is defined as the direction from high potential to low potential.

The international unit system of voltage is volt (V for short), and commonly used units are millivolt mV, microvolt μV, kilovolt kV, etc. This concept is similar to the water pressure caused by the high and low water level. It should be pointed out that the word voltage is generally used only in circuits, while potential difference and potential difference are generally used for all electrical phenomena.

If the magnitude and direction of the voltage do not change with time, it is called steady voltage or constant voltage, which is referred to as DC voltage for short, and is represented by the capital letter U. If the magnitude and direction of the voltage change with time, it is called transformation.

For circuit analysis, one of the most important variable voltages is sinusoidal alternating voltage (AC voltage for short), whose magnitude and direction change periodically according to sinusoidal law with time. The instantaneous value of AC voltage should be represented by lowercase letters u or u(t). The device that provides voltage in the circuit is the power supply.

Voltage law:

Voltage is the reason that drives the directional motion of free charge to form current. The reason why current can flow in the wire is also because there is a difference between high potential and low potential in the current. This difference is called potential difference, also known as voltage. In other words. In a circuit, the potential difference between any two points is called the voltage of these two points. The letter u is usually used to represent voltage.

Series-parallel relation of voltage:

If the elements in the circuit only contain series or parallel connections and are directly connected to the power supply, regardless of the internal resistance of the power supply, the total voltage on the series circuit is equal to the sum of the voltages on all parts of the circuit.

The difference between high pressure and low pressure is:

Based on the voltage value of electrical equipment to ground. The voltage to ground is higher than or equal to 1000 volts. The voltage to ground is lower than 1000 volts.

Among them, safe voltage refers to the voltage that the human body contacts for a long time without the danger of electric shock. According to the national standard "GB3805-83", safe voltage stipulated the voltage series provided by specific power sources to prevent electric shock accidents. China has stipulated the following five grades for power frequency safe voltage, namely, 42V, 36V, 24V, 12V and 6V.