Keep in mind the "Faraday Cage Effect" and it can save your life if you encounter this situation while driving!

Produced by: Science Popularization China

Author: Yiyan Science Team

Producer: China Science Expo

Recently, an incident of a car getting caught on a cable on the road has attracted widespread public attention. The driver did not choose to get off the car, but continued to drive. This behavior seemed irresponsible to some people, but some people said, "Fortunately, the person who got caught was a smart person."

Why is this happening? Isn't the driver afraid of having to pay compensation if he cuts the cable? What is the correct approach in this situation?

Wires fallen on the ground

(Photo source: veer photo gallery)

Saving your life is more important than losing money

If you encounter a scratch while driving on the road, you will usually stop the car and get out to check. However, in some cases, you really can't just get out of the car, and you may even have to continue driving for a distance. For example, if you scratch an electric wire while driving, you must not get out of the car blindly to check.

Power lines above the city

(Photo source: veer photo gallery)

Most of the wires installed in cities are live, and some are even high-voltage cables. The voltage of high-voltage cables is generally above 10kV, and some can even reach 750kV. The voltage that the human body can withstand generally does not exceed 36V, and a current of less than 5 mA flowing through the body for a short time generally does not cause great harm to the human body. However, if you are in contact with current for a long time or your body is wet, there is a risk of electric shock. Therefore, even the lower voltage (220V) transmitted in the city is far beyond the human body's tolerance range.

If you encounter a situation where your car hits an electric wire, it is actually safer to stay in the car. Although the car shell is made of metal, it provides a safe "place" for the human body due to the existence of the Faraday cage effect .

Car Metal Body

(Photo source: veer photo gallery)

A Faraday cage is a closed space made of metal or conductive materials , named after scientist Michael Faraday. The principle is that when an external electric field acts on the Faraday cage, the charges on the surface of the cage will be redistributed to neutralize the effect of the external electric field. At this time, the electric field inside the cage is almost zero, thus protecting the space inside the cage from the influence of the external electric field.

In 2012, an American magician wore a specially made metal coat and helmet weighing more than ten kilograms. He successfully endured continuous electric shocks for 72 hours under a high voltage of 1 million volts, and his body was almost unaffected.

Therefore, when a car hits a cable, the metal body acts as a Faraday cage, effectively preventing the current from passing through the car and harming the people inside.

Faraday cage experiment

(Photo source: veer photo gallery)

If a person touches metal parts in a car, will he get an electric shock? In fact, there is no need to worry. Even if you touch metal parts in a car, the electric potential of the human body is equal to that of the car body, so it is safe inside the car.

The Faraday cage effect is common in everyday life

If you can't find a suitable indoor place to avoid thunderstorms on a rainy day, staying in the car is relatively safe. Even if the car is struck by lightning, the car shell will become a "protective shield" to protect the interior of the car from the impact of lightning. In addition, the current generated by lightning will also be transmitted to the ground through rain and wet tires, making the car a safe place to protect against lightning.

In fact, the Faraday cage is not just about preventing electric shock!

Thunder and Lightning

(Photo source: veer photo gallery)

If you look closely at the structure of a microwave oven, you will see a metal grid on the glass door. What is it for? Microwave ovens mainly rely on microwaves to heat food. The metal shell and the metal grid on the door together form a closed metal space, which is equivalent to a Faraday cage.

This structural design not only helps the propagation of microwaves in the oven, improving the heating efficiency and the uniformity of heating of food, but more importantly, the electromagnetic shielding effect of the metal shell confines the microwaves in the oven, which can effectively prevent potential harm of microwaves to the human body.

Internal structure of microwave oven

(Photo source: veer photo gallery)

Elevators are the most common Faraday cages in our daily lives, and they are also "cages" with relatively good shielding effects. When we enter an elevator, the mobile phone signal is weak, and the "culprit" is also the Faraday cage. The elevator car is made of metal materials. From the moment the door is closed, the elevator is equivalent to a closed environment. When external electromagnetic waves come in, the electrons inside the car will rearrange, offset the influence of external electromagnetic waves, and play a shielding effect.

Elevator shaft

(Photo source: veer photo gallery)

In addition, elevator shafts are mostly reinforced concrete structures, which are equivalent to a large Faraday cage that blocks and absorbs electromagnetic waves. Therefore, it is not difficult to understand why the signal of a mobile phone placed in a "cage within a cage" becomes weak or disappears.

We all know that we shouldn’t touch fallen electrical wires, but we also can’t look at them too closely!

You can't touch it, and you can't go close to look at it. Because we can't be sure whether it is electrified. If it is high voltage, the consequences of touching it can be imagined. So can you go close and use a dry wooden stick to pick up the wire? This is also unsafe. When people approach the point where the wire falls, they will get an electric shock due to the existence of step voltage. Step voltage refers to the voltage between the two feet when a person walks in the area around the point where the ground current enters when an electrical device fails.

Electric sparks from wires

(Photo source: veer photo gallery)

When electric wires (especially those with broken points) fall to the ground, they form a loop with the earth. The current flows through the wires to the earth, so there will be a strong electric field around the grounding point of the wire. If you walk in this area, there will be a voltage difference between your two feet, causing current to flow through the human body and bring the risk of electric shock.

If you encounter this situation, should you just run away with big strides?

You can't run. If you want to leave this dangerous area, you need to hop on one foot or move in small steps with your feet together until you are eight meters away from the point where the wire lands. Because the longer the distance between the two feet, the greater the step voltage, the easier it is to get an electric shock. And after an electric shock, the muscles of the person will spasm, and in severe cases, they will faint. If they fall to the ground, it will be even more dangerous.

Conclusion

Most of the "incomprehension" in life can be explained in a scientific way. Don't panic when encountering an emergency. Stay calm and save your life at the critical moment. As discussed in this article, the Faraday cage principle not only protects the driver's life in certain situations, but also serves as an important window for us to understand electrical safety. Through scientific methods, we can better understand the world around us and make the right decisions when facing potential dangers.

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