Electricity

1
Electricity

• 3.01 Analyze the nature of static electricity and
  the conservation of electrical charges.
• 3.02 Analyze the electrical charging of objects
  due to the transfer of electrons by friction,
  induction, or conduction.
• 3.03 Analyze the direct current of electrical
  circuits.

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Electricity

• Electricity is a form of energy caused by the
  movement of electrons.
• Opposite charges attract Like charges repel.
• Conductors are materials which allow electrons to
  flow through easily.
• Example metals and water plus salts.
• Insulators are materials which do not allow
  electrons to flow through easily.
• Example wood, glass, plastic.
• Objects become charge only by gaining or losing
  electrons Never protons.

3
Types of Electricity

• There are two types of electricity
• 1. Static electricity, and
• 2. Current electricity.
• 1. Static electricity is the transfer of
  electrons from one object to another.
• 2. Current electricity is the continuous flow of
  electrons.

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Static Electricity

• Rubbing generates static electricity.
• 1. When 2 objects rub together, both become
  charged one becomes positive (loses electrons)
  and the other becomes negative (gains electrons).
• 2. Electrostatic Series When any two substances
  listed on the Electrostatic series chart are
  rubbed together, the substance higher on the
  chart will become positively charged and the
  substance lower on the chart will become
  negatively charged. The farther apart the two
  substances on the chart, the greater the charge
  produced.

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Static Electricity

• The Electrostatic Series
• Positive Charge
• Glass
• Nylon
• Wool
• Silk
• Paper
• Wood
• Sealing wax
• Styrofoam
• Rubber
• Plastic wrap
• Negative Charge

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Static Electricity

• 3 Methods of Charging Objects
• 1. The Friction method is rubbing to objects
  together.
• 2. Conduction involves the direct contact of
  objects and is where electrons flow through one
  object to another object.
• 3. Induction involves the rearrangement of
  electric charges a neutral object needs only to
  come close to a charged object, no contact is
  necessary.

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Electric Discharge

• The loss of static electricity as electric
  charges move off an object is called electric
  discharge.

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Electric Discharge

• Most dramatic example of electric discharge of
  static electricity is lightning..
• During a storm particles in the clouds are moved
  about by wind.
• Charges may become separated, and there are
  buildups of positive and negative charges.
• As a negatively charged edge of a cloud passes
  near the Earth, the objects on the Earth and the
  ground surface become positively charged by
  induction.
• Soon electrons jump from the clouds to the Earth
  and this transfer of electrons is called
  lightning.

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Electroscope

• An electroscope is a device used to detect a
  charge on an object.

10
Current Electricity
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Current Electricity

• Resistance of a wire depends on
• 1. Length of the wire,
• 2. Thickness of the wire,
• 3. Temperature of the wire.
• Ohms Law states that the current in a wire (I)
  is equal to the voltage (V) divided by the
  resistance (R). I V/R
  Amperes Volts
• Ohms
  

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Batteries

• A battery is a device that produces electricity
  by converting chemical energy into electrical
  energy.
• Made up of several smaller cells called electric
  cells, or electrochemical cells.
• Each cell consists of two different materials
  called electrodes as well as an electrolyte.
• The electrolyte is a mixture of chemicals that
  produces a chemical reaction.
• The chemical reaction releases electric charges.
• Electric cells can be either dry cells or wet
  cells, depending on the type of electrolyte used.

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Batteries

• Dry cell, such as the battery in a flashlight,
  uses an electrolyte that is a paste-like mixture.
• Made up of a zinc can, a moist paste-like mixture
  of chemicals and a solid carbon rod in the
  center.
• The current flow is from negative to positive.
• Wet cell is a Voltaic cell.
• A car battery is a series of wet cells.
• The parts consists of two different metal plates,
  (electrodes) Zn Cu a conducting liquid (an
  electrolyte), hydrochloric acid, and a conducting
  wire.

14
Thermocouples and Photocells

• A thermocouple is a device that produces
  electrical energy from heat energy.
• Releases electric charges as a result of
  temperature differences.
• Used in thermometers in car engines, ovens, and
  gas furnaces.
• A photocell is a device that uses electrons
  emitted from a metal during the photoelectric
  effect to produce current.

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AC/DC

• AC alternating current and is a current in
  which the electrons change the direction of their
  flow.
• Electricity in our homes and other places is AC.
• A rectifier changes AC to DC by conducting
  current in only one direction.
• An amplifier strengthens the signal.
• DC direct current and is current in which
  electrons flow in one direction.
• For example Batteries

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Electric Circuits

• There are two types of electric circuits
• 1. Series circuits.
• 2. Parallel circuits.

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Electric Circuits

• Series circuits
• Has one path only.
• All loads are connected one after another.
• All loads must share the total current.
• Each bulb added in series decreases the
  brightness (current) of all the bulbs.
• The total resistance is equal to the sum of all
  the resistances in the circuit.
• If one bulb goes out they all go out.

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Electric Circuits

• Parallel circuits
• Has more than one path.
• Each load receives the full current flow
  available (no sharing).
• Each bulb added increases current flow and
  brightness.
• If one bulb goes out, the others stay lit.

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Electric Energy and Power

• Electric Power is a measure of the rate at which
  electricity does work or provides energy.
• Power Voltage times Current P V x I the
  unit is Watts.
• Electric Energy is measured in kilowatt-hours
  (kWh).
• Energy Power x Time E P x t
• One kilowatt-hour is equal to 1000 Watts of power
  used for one hour of time.

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Circuit Safety Features

• Fuses and circuit breakers protect against too
  much current flowing at once through the circuit
  which would cause an overload.
• A fuse is a thin strip of metal used for safety
  because when the current flowing through it
  becomes too high, it melts and breaks the flow of
  electricity.
• A circuit breaker is a reusable device that
  protects a circuit from becoming overloaded.

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Transistors

• Transistors are a sandwich of 3 semiconductor
  crystals used to amplify an electric current or
  signal (make bigger, stronger, or louder).
• Transistors are very small, lightweight, and
  durable.
• Transistors replaced the vacuum tube and had a
  significant effect on electronic devices.

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Integrated Circuits

• Integrated circuits, also known as chips,
  combines many diodes and transistors on a thin
  slice of silicon crystal.
• Cathode Ray Tube produces images on a screen.
• Tungsten metal from which filaments in light
  bulbs are made.
• Induction Coil a device that produces high
  voltage.