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

1. Cell Phone

2. Electricity !!
A general term that
encompasses a variety
of phenomena resulting from
the presence and flow of
electric chargeA

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. 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. 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. 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. 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. Analog and Digital Signals

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. 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. 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. 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. 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. 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