How to Determine Whether the Neutral Wire at Home is Broken?
1. **Detect with a Test Pen** - **Principle**: The working principle of a test pen is that when the tip of the pen touches a charged object, current flows through the neon tube, resistor in the test pen and then into the earth through the human body, forming a loop and making the neon tube glow. Under normal circumstances, in a household electrical circuit, the live wire is charged. When the test pen touches the live wire, the neon tube glows, while the neutral wire is not charged and the neon tube does not glow when the test pen touches the neutral wire.
- **Operation Method and Judgment**: Insert the test pen into the holes of the socket. If the neon tube of the test pen glows in the hole that should be the neutral wire socket, it is very likely that the neutral wire is broken. However, it should be noted that this situation may also be caused by induced electricity, so it is necessary to further judge by combining other methods.
2. **Detect with a Voltmeter** - **Principle**: A voltmeter is an instrument used to measure the voltage across a circuit. In a normal household electrical circuit, the voltage between the live wire and the neutral wire should be about 220V, and the voltage between the neutral wire and the earth should be 0V (because the neutral wire is grounded on the power supply side).
- **Operation Method and Judgment**: Connect one probe of the voltmeter to the earth (this can be done by connecting the probe to a well-grounded object such as a metal water pipe, provided that the grounding body such as the water pipe is itself well connected), and insert the other probe into the neutral wire socket of the socket. If the voltmeter shows a voltage (close to 220V), it indicates that the neutral wire is broken. This is because after the neutral wire is broken, the neutral wire after the break point is connected to the live wire through the load, and there will be a potential difference between it and the earth similar to that between the live wire and the earth.
3. **Observe the Working Status of Electrical Appliances**
- **Principle**: In a household electrical circuit, many electrical appliances rely on the loop formed by the live wire and the neutral wire to work normally. When the neutral wire is broken, the working status of some electrical appliances will become abnormal.
- **Operation Method and Judgment**: If it is found that some electrical appliances cannot work normally, for example, the lights become significantly dimmer or flicker (for some simple lighting fixtures), or the rotational speed of some electrical appliances with motors (such as electric fans, washing machines, etc.) slows down or there are abnormal vibrations. At the same time, when these electrical appliances malfunction, if it is found that the power supply of the live wire is normal, it is possible that the neutral wire is broken. However, the abnormal working status of electrical appliances may also be caused by other reasons, such as the malfunction of the electrical appliances themselves or the instability of the power supply voltage, so further investigation is needed.
4. **Check the Situation Inside the Distribution Box** - **Principle**: Equipment such as air switches and residual current circuit breakers in the household distribution box are connected to the household electrical circuits. If the neutral wire is broken, it may be reflected in the connection parts of these devices or on the neutral wire busbar.
- **Operation Method and Judgment**: Open the distribution box and check whether the connection screws on the neutral wire busbar are loose or whether there are signs such as charring or breakage of the neutral wire conductors. Meanwhile, observe the wire conditions of each branch connected to the neutral wire. If it is found that the neutral wire of a certain branch is abnormal, it may be that the neutral wire of that branch is broken.
