# How Can You Stop Electromagnetic Radiation From Penetrating a certain area?

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#### Updated on May 02, 2013

##### Type

Physics (electromagnetism)

##### Difficulty of Project

Difficult (due to math)

\$3

None

##### Material Availability

Easily available from the drugstore or your home.

### Objective

• To understand Gauss' law and its implications.
• To be able to calculate and comprehend the flow of electrical charges in a Faraday Cage.
• Tin Foil
• A cell phone

### Introduction

Gauss' law states that the electric flux through any closed surface is proportional to the enclosed electric charge.This law has many implications, including one which Faraday discovered.In a “Faraday Cage”, or an ungrounded enclosure formed by conducting material, the outside of the enclosure holds an electric charge, but anything inside the enclosure holds none.

##### Research Questions

How does Gauss' law prove the existence of Faraday Cages?

##### Terms, Concepts and Questions to Start Background Research
• What is a surface integral?How does it differ from a normal integral?
• What is the total charge emitted when making a cell phone call?
• What is the electric constant?

1. First, begin with the demonstration.
2. Wrap a cell phone in tin foil.
3. Attempt to make a call.
4. Do you hear it ringing?That is because of the Faraday cage!
5. Calculate the reason that this occurs.
6. Find the formula for Gauss' law.
7. Using the formula, calculate the electric flux through the aluminum foil.
8. Now, using the formula, calculate the electric flux inside the aluminum foil.

### Bibliography

Nave, R. Gauss' Law.Hyperphysics.Georgia State University, Department of Physics and Astronomy.2001. http://hyperphysics.phy-astr.gsu.edu/HBASE/electric/gaulaw.html

Paul's Online Math Notes.Surface Integrals. 2010. http://tutorial.math.lamar.edu/Classes/CalcIII/SurfaceIntegrals.aspx

A graduate of Brandeis University, Sharon Cooper loves anything having to do with English, History, and Creative Writing. When she is not creating science fair ideas, she is translating Chaucer, writing short stories, or reading various works of literature. To discuss literature or literary experimentation, please contact Sharon at secooper87@gmail.com.