Shielding and the Faraday cage

Low-intensity electric fields are almost always present in our environment. Every wire in your house generates electric fields, as does every atmospheric lightning bolt. Cellphones, wireless networks, and radios are sensitive to these fields. Dropped cellphone calls and static are partially caused by interference from stray electric fields. Fortunately, there is a way to shield against stray electromagnetic fields. Read the text aloud
Shielding of electric fields by a conductorAn electrical conductor, such as a metal, is a material in which charges are free to move. Consider what happens to a conductor placed in an electric field. Because they can move, charges feel the electric force and respond by moving almost instantly. The charges rearrange themselves so that the electric field inside the conductor is zero!

Why is the field inside zero?
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The field is zero because, if it were not zero, the charges in the conductor would continue to feel electric forces and continue to move in response. The charges in a conductor only stop moving when there is no longer any electrical force acting on them. When the electric force is zero inside the conductor, the rearranged charges have created an additional electric field that exactly cancels out the external electric field. This effect is called shielding. Read the text aloud Show Gauss’s law
Shielding on a computer cable blocks outside electric fieldsComputer network signals can be corrupted by stray electric fields. To prevent this from happening, all computer network cables have a conducting metal layer surrounding the signal wires inside. The metal layer shields the wires from stray electric fields. Read the text aloud
The English scientist Michael Faraday in 1836 invented the Faraday cage. A Faraday cage is made of a conductor and uses the shielding effect to protect whatever is inside from external electricity and electric fields. A Faraday cage can be struck directly by lightning, yet a person inside is completely safe. Read the text aloud
What happens when lightning strikes a carIf you are driving through a lightning storm, the safest place to be is inside a metal car. The reason is not that the car’s rubber tires are insulators. The correct reason is that the car’s metal shell is a Faraday cage. If lightning were to strike the car, electric charge would redistribute itself around the outside of the car’s metal shell to cancel out the electric field inside the car, leaving the interior safe. Read the text aloud
Imagine zapping a metal sphere with a million volts of electricity. How does the electric field inside the sphere differ if the sphere is hollow versus solid? Show

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