Work in Electrical Systems

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Work in Electrical Systems

• Notes 2.3

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• Forces are applied to charged objects by electric
  fieldselectric fields are created by other
  charges. You cant see or hear electrical work,
  you can only see the results of the work because
  it is converted into other forms of energy such
  as rotation, light, sound, and heat.

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• I. Coulombs
• A. 1 electron 1.6 x 10-19 C
• B. 1 C charge of 6.25 x 1018 electrons
• C. the net charge of 1 coulomb 6.25 billion
  billion
• electrons on the bottom plate of a capacitor
  rather than on the top plate.

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• II. Work in Electrical Systems
• A. E FE/q (electric field equals force
  divided by charge)
• B. When a charge is moved in an electric field,
  work is done.
• C. ?V E x d (change in voltage equals
  electric field times distance moved)

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• D. W ?V x q (Work equals change in voltage
  times charge)electrical work is the product of
  potential difference and charge moved.
• E. 1V 1 J/C ( One Volt 1 Joule per Coulomb)
• F. vectors point away from the positive charge
  and toward the negative chargework can be
  positive or negative

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• III. Electric Charge and Current
• A. 1A 1C/s ( One Ampere equals one Coulomb
  per second)
• B. I q/?t (Current equals charge divided by
  change in time)
• C. 1C 1 As (1 Coulomb equals 1
  amperesecond)
• D. 1 amperehour 3600 coulombs

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• IV. Effects of Electrical Work
• A. movement
• B. thermal energy
• C. light
• D. sound

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• V. Efficiency of Electrical Devices
• A. E ow/iw
• B. Not all electrical work is converted into
  mechanical work therefore, no electrical device
  can ever be 100 efficient.

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• VI. Why Use Electricity to Do Work?
• A. Produced by
• 1. burning coal, gas, or oil to produce
  thermal energy
• 2. thermal energy converts water into
  high-pressure steam
• 3. steam pressure is used to drive turbines
• 4. turbines drive electrical generators to
  produce electricity

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• B. Reasons for using electricity
• 1. affordable
• 2. can move over long distances through
  overhead or underground wires
• 3. can be transformed into other forms of
  energy and work
• 4. convenient and easy to use