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Are you still thinking that current flows from live to neutral?You may be a fake electronics engineer

We know that alternating current flows through the live wire to the neutral wire, and then flows from the neutral wire to the live wire all at once. So why is it that we are not electrocuted when we touch the neutral wire, but are electrocuted when we touch the live wire? Some friends began to wonder, in the power system, how does the current flow in the AC circuit?

We know that alternating current flows through the live wire to the neutral wire, and then flows from the neutral wire to the live wire all at once. So why is it that we are not electrocuted when we touch the neutral wire, but are electrocuted when we touch the live wire? Some friends began to wonder, in the power system, how does the current flow in the AC circuit?

To answer this question, we should have to start with the power supply system, as shown in the figure below, which is the TN-S power supply system commonly used in our daily life.

Are you still thinking that current flows from live to neutral?You may be a fake electronics engineer

TN-S power supply system

In the TN-S power supply system in the figure, we know that the neutral line on the low-voltage side of the transformer has been grounded. If the earth is used as a reference, the potential of the zero line and the earth is zero from beginning to end.

That way, when we’re standing on the ground, we’re at the same point with the zero line. Therefore, there will be no potential difference, which is what we call voltage, and there is no possibility of electric shock. However, the situation with the live wire and the neutral wire is quite different.

Next, let’s take a look at the waveform of the alternating current, as shown in Figure 1 below. In this circuit, how does the current flow? From this figure we can observe that when at 0, the current is also zero.

Are you still thinking that current flows from live to neutral?You may be a fake electronics engineer

But at time 0, no current flows through the circuit in Figure 2.

Are you still thinking that current flows from live to neutral?You may be a fake electronics engineer
Figure II

In the time period of 0-1, the current in Figure 1 will increase with the passage of time, and more importantly, when it reaches the moment of 1, the current has even reached a peak value.

But at this moment in Figure 2, the current flows from the fire line L to -2-3-N (zero line), and it is always in a state of increasing.

With the passage of time, at the moment of 1-2, the current in Figure 1 begins to gradually decrease. However, the direction is still in the same state, and even when the moment 2 is reached, the current has been reduced to zero.

However, at this time in Figure 2, the current flow still does not change, it is still from L (live wire)–2–3–N (neutral wire), and the current is slowly decreasing.

During this time period of 2-3, the current in the figure has gradually become a negative number, and this value is getting smaller and smaller. When it reaches the moment of 3, the current has reached the peak value of the value.

In Figure 2, the current is from N (neutral line) – 3 – 2 – L (live wire), and it is always in a state of increasing.

3-4 During this time period, the current in Figure 1 gradually decreases in the opposite direction, and at time 4, the current is zero. At this time, the current direction in Figure 2 is from N (neutral wire) – 3 – 2 – L (live wire).

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