About the confusion of AC live wire and neutral line, the master advances

This issue is actually very complex, and it is necessary to make it clear from several aspects.

1.Alternating current is essentially a live wire and a neutral wire. The neutral wire is actually a wire that has nothing, like a copper wire you just bought from a hardware store. It's not grounded, one end is connected to your outlet, and the other end is measured on the meter.

The ground is the one on the three sockets.

2.The live wire voltage is 220V, which is 220V - 0 - 220V back and forth. The neutral voltage is always 0, so an alternating current is formed.

Of course, in the case of not connecting electrical appliances, the neutral line will naturally not have voltage, that is, the voltage tester light will not be on.

3.Regarding the current, the main thing to look at is the magnitude of the resistance, Ohm's law i u r. It's not the same as the flow of water. When you determine a value for the resistor, the current is determined since the voltage is always 220V. There is no such thing as "excess current".

If it is not working with electrical appliances, there is no current in the circuit.

If your level matches the question you asked, you can refer to the junior high school physics textbook and start from scratch (electricity section). Definitely better than those blunt professional reads.

The voltage is relative, the live wire is 220V relative to the neutral line and the ground, and the neutral line is 0V voltage relative to the ground.

The 220V AC voltage only changes sinusoidally on the live wire, and the neutral line is always grounded.

Summary. Misunderstanding, the communication is not positive or negative, it is the line of fire, the zero line, not constantly changing, only the line of fire is connected through an electrical appliance and change, there will be changes, such as the bulb, a second frequency of 50, positive 50 also lights up the bulb, negative 50 also lights up the bulb, the current is only connected to the general electrical appliances will work, in fact, electricity and water are the same, electricity through the wire zhidao and electrical appliances, like a light bulb, water through the pipe and water device, the positive and negative poles of the alternating current are constantly changing, That is to say, the current will flow from the live wire to the neutral wire, and from the neutral line to the live wire, and flow back and forth. That's right.

Hello, the positive and negative poles of alternating current are constantly changing, that is to say, the current will flow from the live wire to the neutral wire, and from the zero line to the live wire, back and forth. Staring at Pei Xi is this Kai like Kaihu.

Misunderstood, the surplus flow is not positive or negative, is the line of fire, the zero line, not constantly changing, only the line of fire through an electrical appliance and change communication, there will be changes, such as light bulbs, a second frequency of 50, positive 50 also light up the bulb, negative 50 also light up the bulb, the current is only in the case of the general electrical appliances will work, in fact, electricity and water are the same, electricity through the wire zhidao and electrical appliances vertical shed connection, like a light bulb, water through the pipe and water applicator communication, sincerely answer every question for you! If you are satisfied, it is the best! If you have any questions, please keep asking!

Have a great day! Happy every day.

It used to be liveline! Access to the common neutral line and the neutral line is live.

There are many wiring rules that require the identification of live wire and neutral wire, such as left zero and right fire, live wire over switch, live wire lamp core, etc. The neutral line is used to make the live wire Jiankai ridge circuit, and it must go to the neutral point of the transformer. The ground wire is used to prevent people from being electrocuted, and it must be blocked by a good grounding device.

Therefore, for electrical equipment with metal body shells, especially movable equipment, it is generally not allowed to connect zero ground wires in parallel. If the grounding is very reliable, the neutral line can be connected to the ground wire, but the neutral line loop must be the neutral point of the transformer (or the neutral line outlet), and the ground wire must not be used as a neutral line loop. Some people mistakenly think that the zero wire is the ground wire, and connect the grounding of household appliances with the zero wire, so the live wire forms a loop with the zero line at the same time as it forms a loop with the shell of the household appliances, so that the shell is electrified, especially in the case that the zero line has been disconnected due to a fault and the power socket is not well grounded, it is easier to be electrocuted.

Get to know alternating current

Alternating current refers to the current whose direction changes periodically over time, with an average current of zero in a cycle. Unlike direct current, which changes its direction over time, direct current does not change periodically.

Usually, alternating current (AC) waveforms are sinusoidal. Alternating current can transmit electricity efficiently. But there are actually other waveforms that are used, such as triangular waves, square waves.

The mains power used in daily life is alternating current with a sinusoidal waveform. Let's take a look at the characteristics of alternating current from the figure below.

The voltage value periodically changes in magnitude and direction.

In China, the weekly bear of the specified AC voltage value is 20 milliseconds. From the perspective of the external circuit, when 0-10 milliseconds, the voltage is positive, and the current flows from the terminal XT1 to the resistance R, and then returns to the power supply through the terminal XT2 At 10-20 milliseconds, the voltage is negative, and the current flows from XT2 to R, and then returns to the power supply through XT1.

Because of this characteristic, some people think that there is no definition of the wire number, because the current runs from the live wire to the zero line for a while, and then slips from the zero line to the live line, so why divide it into two concepts? There shouldn't be a line of fire and a line of zero, right? This brings us to a discussion about how the power supply came about.

The figure below is ** on the network).

First of all, we need to know that this is true for single-phase generators. But the source of electricity used in our homes is a three-phase generator, which is symmetrical, with a phase difference of 120° and equal size. Due to the high voltage level of the generator output, so through the power supply line, and finally to our users, the transformer in the substation and distribution room needs to reduce its voltage to 380V, and the secondary side of the transformer is also A, B, C three-phase power supply, the interphase voltage is 380V, that is, what we call the live line.

The neutral line is extracted from the neutral point of the transformer, and theoretically the voltage at the neutral point is 0V, because the sum of the voltage vectors of the three-phase power supply at each moment is 0V. In this way, the voltage between each relative neutral line of A, B and C is 220V, which is the user's guaranteed power voltage. However, in order to ensure a constant voltage for the user, the neutral point of the transformer is forced to be grounded, the so-called working ground.

In this way, even if the three-phase load is asymmetrical, there will be no drift of the neutral point to the ground voltage.

Therefore, the electricity used by our users is divided into live wire and neutral wire.

The so-called neutral line and live wire are actually the concept of alternating current, which is derived from the concept of phase wire and neutral wire. Most modern alternating currents use three-phase alternators to generate electricity, and the three-phase alternating current it produces has three phase wires and one neutral wire. The neutral wire is connected to the earth, and the potential of the neutral wire is equal to the earth at any time, or the potential difference is zero, so the neutral wire is called the neutral wire or ground wire.

After the neutral wire is connected with the earth, the other three phase wires have a potential difference with the neutral wire, or they are electrified, so people call it the fire wire.

For direct current, if a DC circuit is not grounded, there is theoretically no potential difference with the earth, that is to say, there is no such thing as the so-called zero wire and live wire. In the DC power supply circuit, one end of the power supply is generally connected to the earth, and after being connected to the earth, this wire is called the neutral line or ground wire, and the wire that is not connected to the earth is called the live wire because of the potential difference between it and the earth (note that the live wire here actually represents the line with the potential difference, and the potential difference may be positive or negative), as shown in Figure 1 below. The red line can be called the live wire, and the negative part of the battery to the left end of the lamp is the neutral line.

2. The blue part of Figure 2 below (although it is the positive pole of the power supply, but because it is connected to the earth, it has to be called) is called the neutral line, and the part from the negative pole of the power supply to the left end of the lamp is called the live wire (although the potential difference between it and the earth is negative, but because there is a potential difference between it and the earth, or it is electrified, it is called the live wire).

The section of the correct red line is the live wire, and the one on the live wire has voltage. If that switch is closed, there is voltage all over the line.

Wrong. The live wire refers to the line with the voltage to the ground in the mains (alternating current), and the power icon in the figure is direct current, and the live wire is only the voltage positive lead, not called the live wire.

Personally, I think this circuit is done right, the switch is installed in front of the electrical equipment, so that there will be no accidental electric shock accident, from an electrical point of view, the regular circuit laying and installation process stipulates that the live wire can not be installed with control switches and fuses, and the installation position of this circuit switch also conforms to such a rule.

The transmission of mains power is in a three-phase way, and there is a neutral wire, and the current of the neutral wire is zero when the three-phase is balanced, commonly known as it"Zero line"Another feature of the neutral wire is that it is short-circuited with the ground wire in the total distribution input of the system, and the voltage difference is close to zero. The three phase wires and the neutral line of three-phase electricity have a voltage of 220, which will produce electric shock to people, commonly known as it"Fireline"。

That's right, generally speaking, the switch is installed in the direction of the live wire.

This circuit is a DC circuit, and there is no zero live wire for DC circuits.

The power cord used in the general household is composed of two wires, one of which is called the phase wire (commonly known as the live wire) and the other is called the neutral wire (that is, the neutral wire). Under normal circumstances, the neutral potential is zero, and the voltage between the phase and neutral is 220 volts. The neutral line is generally directly connected to the earth, so the potential of the neutral line and the earth is equal.

The standard single-phase user has three wires, phase line L, neutral line N and ground wire PE, neutral line N and phase wire of the same cross-section, ground wire PE is square millimeters, double color).

The neutral wire is always equipotential to the earth, so a complete period of the live wire of an alternating current is that if it is the same as the neutral potential at 0 seconds, the voltage of the live wire to ground is 0; After a few seconds, the voltage to the ground on the live wire reaches a maximum of 318V above the ground; After another second, the voltage on the live wire to the ground drops to 0 again; After another second, the voltage on the live line to the ground dropped to the lowest point, which was 318V lower than the ground; After another second, it rises again to the same potential as the neutral line, and the voltage to ground on the live wire is 0.

It can be seen that although the alternating current changes the direction of the current periodically, the voltage of the neutral line to ground is always the same, which is 0. After connecting the electrical appliances, there is a current on the neutral line, and the current change law is the same as the voltage.

Because the voltage of alternating current is AC, positive for a while and negative for a while, so it is impossible to distinguish between positive and negative poles, live wire and ground wire are another thing, the power plant sends out three-phase electricity, there are four wires, three with the live wire and one with the ground wire, the alternating current we usually use is any one with the live wire and that ground wire, you can see 4 parallel wires on the pole on the road, this is the three-phase four-wire system. It is divided into A, B, C, N, regardless of ABC, the voltage between the three wires is called the phase voltage of 380 volts, and AN or BN or CN is connected to the live wire and neutral line of your home, which is 220 volts.

Because it's alternating current, alternating current. Alternate changes.

The zero line is connected to the earth, and the potential difference between it and the earth is 0vThe other wire is not connected to the earth, and the potential difference between it and the earth is 220V, and this wire is the live wire.

For three-phase power supply, due to the phase difference of the three-phase current of 120 °, if the load of each phase is balanced, the result of the superposition of the three-phase current is zero, but the absolute balance does not exist, so there is still a current on the zero line, but it is generally much smaller than the line current, and the current on the zero line will not be greater than the current on any phase, which is why the wire diameter of the four-core low-voltage cable is always smaller.

For single-phase power supply, the current of the live wire and the neutral line should be exactly the same, otherwise there will be a leakage imagination, and it is easy to have leakage injury accidents, leakage protectors.

and so-called residual current protectors.

It is by using this principle that the power supply is automatically cut off when the current is not equal.

That's because the neutral line has been well grounded at the place where it is drawn from the power supply transformer, so the voltage between the neutral line and the ground is equal to zero, that is, the neutral line and the earth are equipotential, just like the same wire, and the live wire has a potential difference of 220 between the ground and the earth because of the grounding of the neutral line, which is the voltage, so the electricity on the live wire can not only flow back to the transformer through the neutral line, but also flow back to the transformer through the earth in any possible place. This loop current formed through the ground is called leakage current, and if the line is very long and there are many leakage points, we can measure the difference in the current size between the zero live wire from the closer to the power supply.