Why is the hot wire always bright when using a test pen?
Use a test pen to measure the live wire because the voltage between the live wire and the ground is 220V. When measuring, the live wire passes through the resistance in the test pen and is grounded through the human body. At this time, current will flow, so the light will turn on. The voltage of the neutral line to the ground is zero volts, because the neutral line itself is connected to the earth and is at the same potential as the earth where you are, so there is no potential difference and no current can be formed, so it naturally does not light up.
Why is the neutral line zero? This is because it is grounded. The prescribed potential of the earth is zero, so naturally the potential of the neutral line is zero. This is also the reason why the human body will not get an electric shock when standing on the ground and grabbing the neutral wire.
The neutral line is the line drawn from the neutral point of the transformer. It is the loop from the live wire to the electrical appliances. When the neutral line is drawn out at the midpoint of the transformer, it will be grounded, so you can think of the neutral line as the ground where the transformer is located in the distance, and the home The ground wire in is the protective ground where your home is located. Because the earth is also resistive, sometimes the neutral line in the home will be charged, but the voltage is very small and will not cause personal danger.
The potential of the live wire in the positive half cycle is higher than the zero line, and the potential of the live wire in the negative half cycle is lower than the zero line. The water flows to the lower place, and the current does the same. Here we need to correct a misunderstanding. Many people think that the current can only flow from the positive pole to the negative pole. In fact, the current also flows from the positive pole to the negative pole. The positive electrode with high potential flows to the positive electrode with low potential
The person who asked this question may not understand the electric potential mentioned here. If not, it can also be understood as voltage. In fact, it is not the same concept. Voltage is the electric potential difference. Assuming that the electric potential is the height, the voltage is the height difference. For example, there are two mountains on the mountain. There are two reservoirs, one 100 meters (electric potential) and one 150 meters (electric potential), then their height difference (voltage) is 50 meters. If two reservoirs are connected, the higher water will flow to the lower one. If they are both 150 meters (electric potential) ) would not be able to flow (voltage is zero), even if their height (potential) is high
If you understand the above, the potential of the neutral line is assumed to be the well surface, and the height is fixed. The live line is a bucket filled with water, and the height is variable. When the bucket is above the well surface, the water will flow to the well surface, and vice versa. flow to bucket
Why does the electric test pen light up on the live wire but not on the neutral line? The top of the electric test pen needs to be connected to the human body and then to the earth, and the neutral line is also connected to the earth. Their potentials are the same.
