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# Cellphone (student preso)

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student presentation
general physics 1
presentation 3 group 1
electricity in our daily lives
7 mar 2009

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### Cellphone (student preso)

1. 1. Cell Phone
2. 2. Electricity !! A general term that encompasses a variety of phenomena resulting from the presence and flow of electric chargeA
3. 3. Electricity !! Electric charge – a property of some subatomic particles, which determines their electromagnetic interactions. Electrically charged matter is influenced by, and produces, electromagnetic fields. Electric current – a movement or flow of electrically charged particles, typically measured in amperes.
4. 4. Electricity !! Electric field – an influence produced by an electric charge on other charges in its vicinity. Electric potential – the capacity of an electric field to do work, typically measured in volts. Electromagnetism – a fundamental interaction between the magnetic field and the presence and motion of an electric
5. 5. Cell Phone what is a cell phone? Cell phones are defined as sophisticated radios. They are a type of wireless communication device that uses many small cells with a base station and a cell phone tower at the center of each cell. These cells have extensive frequencies that allow thousands of people to use cell phones at the same time.
6. 6. Cell Phone How Cell Phones Work The cell phone system divides an area of service into a set of cells on what might look like a hexagonal grid. A phone tower or base station in the center of the cell covers an area of 2 or 3 square miles around the tower. Cell phones transmit to towers, which then connects you to the normal land based telephone system to route the call.
7. 7. Cell Phone Analog and Digital Signals An analog signal has a base carrier's radio frequency signal, which is modified in some way to amplify the strength of the signal or vary the frequency to add information to the signal. An analog signal can be represented as a series signal to a signal carrier known as sine waves because carrier waves are analogous to the fluctuations of the human voice or other sound that is being transmitted.
8. 8. Analog and Digital Signals
9. 9. Cell Phone How Does Cell Phone Voice Mail Work? The normal human ear can perceive sound ranging in frequency from 20 to 20,000 Hz.
10. 10. How Does Cell Phone Voice Mail Work? When you use electricity to excite particles in the air, you create waves. The electromagnetic spectrum is just like a rainbow filled with different types of energy waves. Waves used to send text or voice mail messages run well within this spectrum. Cell phones can receive either text (e-mail) or audio messages by using ASCII coding. With digital cell phone voice mail, this is the coding that is used to place the 1s and 0s, or quot;binary streams,quot; onto a carrier wave.
11. 11. How Does Cell Phone Voice Mail Work? Cell phone voice mail is used to catch and record information sent on a carrier signal wave By sending an electrical current through a power source, like a power outlet or battery, cell phones can convert carrier waves into electrical pulses. Then converts those electrical impulses into sound.
12. 12. How Does Cell Phone Voice Mail Work? When you hear sound, your ears are responding to tiny, rapid changes in the pressure of the air. These changes are called sound waves. They can have a single frequency and constant amplitude. Hearing is a complex mixture of waves with different frequencies and amplitudes. Sound waves range from pure sine waves to complex combinations of waves.
13. 13. How Does Cell Phone Voice Mail Work? You can understand what someone says to you on a cell phone voice mail message, because electronic impulses get turned into collections of sounds. A cell phone converts information streams it receives by matching vibrations. Electronic impulses get turned into collections of sounds
14. 14. References http://www.eia.doe.gov/kids/energyfacts/ sources/electricity.html http://www.ehow.com/how- does_4564560_cell-phone-voice-mail- work.html www.yale.edu http://en.wikipedia.org/wiki/Electricity