Static Electricity

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Static Electricity
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Static Electricity

• Electric Charge
• A property of matter having an
• excess of electrons negative
• Deficiency of electrons positive
• Static Electricity
• Electric charges that are stationary
• Electrostatics
• Study of electrical charges that move very little

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Static Electricity

• Neutral
• Electrons are neither positive or negative
• Insulators
• Material that does not allow electric charges or
  heat to move through them
• Conductors
• Material that allows electric charges or heat to
  move through it easily

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LAW OF ATTRACTION AND REPULSION

• Law of Attraction and Repulsion
• Like charges repel and unlike charges attract

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Static Electricity
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Gaining and Losing Electrons

• All matter consists of atoms that have neutrons
  and protons in their nuclei and electrons in the
  energy shells outside
• Some elements hold their electrons (noble gases)
  while others are easily removed (alkali metals)
• Friction is an easy way to remove electrons

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Gain and Losing Electrons

• Positively charged protons remain in the one
  place.
• Either the electrons are lost- and turn positive
  or they are gained and turn negative

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Grounding

• Ground to connect a conductor directly into the
  ground
• Draw diagram for ground

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Grounding

• Earth is a fair conductor of electricity so it
  will accept the excess electrons
• To remove excess electrons from your apparatus
  you attach a wire (conductor) deep into the
  ground
• Ex. Pour a cup of water into the ocean
• No noticeable effect

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Grounding

• Electronic instruments (computers) very sensitive
  to surges of electrical energy which could cause
  a SPARK and start a fire
• Help desk
• rub padding on a wooden table
• grounding wire attach to their wrist

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Controlling Static Electricity

• Lightning
• flash of bright light caused by a discharge of
  electricity between clouds
• negative charges collect in the bottom of a
  cloud (positive on the top) and they repel the
  electrons on the surface of the earth
• leaving the ground positively charged below
  the cloud
• the process- spark

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Lightning

• The process is more likely to happen over th
  highest point on the ground
• Lightning takes the shortest route to earth
• Chain of ions forms and a large discharge occurs
  between cloud and ground
• As it travels through the air it lights up and
  Heats up!
• 65 of all lightning bolts go from one cloud to
  another

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Lightning

• The temp. of the air near a lightning bolt
  reaches up to 33 000 degrees Celsius
• (hotter than the suns surface)
• Air molecules colliding with more air molecules
  produce a shock wave THUNDER
• Heat- causes fire due to high temp

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Lightning Rods

• Lightning Rod
• Metal rod attached to a building to prevent
  lightning damage by conducting the electrons into
  the ground
• It attracts the negative ions that have formed in
  the air and the cloud attracts the positive
• The electrons are carried through the wire on the
  outside of the building (insulated by a rub
  covering) the electrons are transported deep into
  the ground

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Draw Lightning Rod Diagram
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Circuits

• Positive terminal ()
• In a battery the source having a deficiency in
  electrons
• Negative terminal (-)
• In a battery the source having an excess in
  electrons
• Circuit
• Path over which an electric current flows

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Circuits

• Switch
• Device for turning electric current on and off
  (Closing and opening a circuit)
• Circuit Diagram
• diagram that shows a path over which an electric
  current flows
• Battery
• combination of electric cells that produce
  potential difference

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• Resistor
• component that resists the passage of a current
• Load
• a device that resists the flow of current and
  converts electrical energy into other forms
  (light bulb)
• Current
• flow of electric charge

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Draw Circuit Symbols
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Symbols and SI units

• Symbol SI Unit
• Charge Q C (coulomb)
• Current I A (ampere)
• Time t s (seconds)

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Current

• A current of 1.0A 1.0C of charge is moving
  past a point in a circuit every second
• Ammeter measure electric current

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Household Items

• Appliance Current (A)
• Radio .4
• 100w lamp .8
• TV 1.7
• Toaster 8.8
• Microwave 11.7
• Kettle 12.5

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Example Problem

• If 240 C of charge pass a point conductor in 5.0
  min, what is the current through the point in the
  conductor?

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Answer

• Given
• Q 240 C
• t 5 min
• Required to find current (I)
• I Q/t

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Answer

• t 5.0 min
• 300s
• I Q/t
• 240 C .80A
• 300 s

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Current Formula

• I Q/t
• Current charge moving past a point
• time

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Energizing

• Electrons in a battery are energized by
  chemical reactions
• Electrical Potential Energy
• -electric energy stored in a battery
• -cannot produce energy until the battery is
  connected to a load (light bulb) and the
  circuit is closed

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Energy

• All forms of energy measured in Joules
• Voltmeter
• an instrument for measuring the potential
  difference between two points in an electric
  circuit

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Electric Circuit and Water Circuit

• Water Circuit
• pump lifts water to a higher level against the
  pull of gravity
• A valve at the top of the pipe controls whether
  the water will run down
• When water runs down, it turns the waterwheel

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Electric Circuit and Water Circuit

• Electric Circuit
• The battery raises electrons to a higher
  potential energy level at the negative terminal
  (compared to positive terminal)
• The switch determines whether or not electrons
  are allowed to flow in electric energy
• When the electrons flow, current runs to a motor
  and causes it to turn

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Symbols for Potential Energy

• Symbol Unit
• Energy E J (joules)
• Charge Q C (coulomb)
• Potential V V (volts)
• Difference

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Potential Difference

• V J /C
• Volts energy
• charge

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