Question

The top of the atmosphere is at about $400KV$ with respect to the surface of the earth, corresponding to an electric field that decreases with altitude. Near the surface of the earth, the field is about$100\;V{m^{ - 1}}$. Still, we do not get an electric shock as we step out of our house into the open because (assume the house to be a steel cage so that there is no field inside)
A. There is a potential difference between our body and the ground.
B. $100V{m^{ - 1}}$is not a high electric field so that we do not feel the shock
C. Our body and the ground forms the equipotential surface
D. The dry atmosphere is not a conductor

Answer 1

Hint To solve this question we will use the concept of equipotential surface. First of all, you have to understand what is an equipotential surface and what happens at an equipotential surface, how charge travels in it. After understanding these concepts, you will get your answer.

Complete step-by-step solution :To understand and solve this question, let us first learn what is an equipotential surface.
Equipotential surface: When, on any surface the difference between the potential between two points is zero we call it equipotential surface. Or in another word, we can say that if in a surface all the points are in the same potential it is called equipotential surface.
As we know, current only flows in as circuit or surface when there is potential difference between the points. It means, when the potential difference between two points is zero, there would be no current flow.
So, now as per the question, when we are inside the room our body and ground are at the same potential as they are in contact. Now, when we step out of the room in the open, the surface of air covering our body potentially changes to potential equal to our body. Now since the body and the air surface surrounding it are at the same potential. There would be current flow between the air and the body and hence we won’t feel any kind of electric shock.

Note Remember, work done in moving a charge from one position to another in an equipotential surface is always zero. And note that, even if two different bodies have the same potential, current flow across them would also be zero.