Lightning occurs when there is a flow of electric charge (principally electrons) between the ground and a thundercloud. the maximum rate of charge flow in a lightning bolt is about 20,000c/s; this lasts for 100μs or less. how much charge flows between the ground and the cloud in this time?

2C  charge will flow from ground and cloud

Explanation:

We have given rate rate of flow of charge

Time is given as

WE have to find the how much charge flows between the ground and cloud in this time

So the charge flow is given by

So 2C  charge will flow from ground and cloud

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia