Faraday Cage : Why Are Cars & Planes Safe From Lighting
Have you ever wondered if you could survive if you were struck by lightning while you were in your car? In fact, most of the cars are safe from lighting. In this article I will discuss about why are cars and planes safe from lighting and how does electrostatic shielding work.
A car or a plane which has a full metal body essentially acts as a Faraday Cage. In order to understand what is a Faraday Cage, lets dive into electrostatics.
If a conductor is placed in an external electric field, the net electric field inside a conductor always remains zero. Conductors have free electrons which can move freely inside a conductor. These electrons are called free electrons. These free electrons are from the outermost electron shell of the atoms. As the electrons are separated from atoms, the atoms become positively charged.
So, when an external electric field E is applied on a conductor, the free electrons start moving in the opposite direction of the electric field due to the coulomb’s force F = E*q , where q is the charge of the electron.
So, these electrons come together at one end creating negatively charged area. On the other side, the lack of electrons create a positively charged area.
This newly formed charge creates an electric field inside the conductor Eᵢ.
This new electric field Eᵢ and the external electric field E cancels each other. Thus the net electric field inside a conductor becomes zero.
Thus, there can be no electric field inside a metal and also all charges stays on the surface of a conductor. There can be no charge can be inside a conductor. If there is any charge inside a conductor , then we can create a Gaussian Surface inside a conductor which encloses the charges.
As the net charge inside the Gaussian Surface is not zero, the net flux φ is not zero. But as we discussed earlier, the electric field E inside a conductor is zero. So,according to Gauss’s Law, the net flux must be zero. So, the net charge will also be zero inside the Gaussian Surface. If you are not familiar with Gauss’s Law, you can read this article from the link below :
So when a full metallic body like a metallic box is electrified or given any external charge, its inside remains unchanged. No charge can reach inside a metallic box. So, if anybody stays inside a full metallic box, he will be safe even if the box is electrified from outside. This full metal box is called Faraday Cage.
So, as a car of a plane has a full metal body, it works as a Faraday Cage. So if a lighting strikes a car or plane, anyone staying inside it will be safe. Because no electric charge can reach who is staying inside. So a full metal house is always safe from lighting. This principle is used in cases where anything needs to be shielded from electric charge.
