Electricity, Sound and Light

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Electricity, Sound and Light
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Chapter Eight Electricity and Magnetism

• 8.1 Electricity
• 8.2 Electrical Circuits and Electrical
  Power
• 8.3 Properties of Magnets

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Investigation 8A
Electricity

• How does electricity work?

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8.1 Electric and magnetic forces

• All matter has electrical (and magnetic)
  properties because the atoms that make up matter
  are held together by electromagnetic forces.

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8.1 Electric and magnetic forces

• Magnetic forces can attract or repel because
  there are two kinds of magnetic poles, called
  north and south.
• A north pole repels another north pole but
  attracts a south pole.

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8.1 Electric and magnetic forces

• Like magnetism, electric charge comes in two
  types. We call them positive and negative.
• A positive charge attracts a negative charge and
  vice versa.
• Two similar charges repel each other.

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8.1 Electric charge

• Electric charge, like mass, is also fundamental
  property of matter.
• Inside atoms found in matter, attraction between
  positive and negative charges holds the atoms
  together.

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8.1 Electric charge

• Because ordinary matter has zero (total) charge,
  most matter acts as if there is no electric
  charge at all.
• A tiny imbalance in either positive or negative
  charge is the cause of static electricity.

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8.1 Electric current

• Electric current is caused by moving electric
  charge.
• Electric current comes from the motion of
  electric charges that are much smaller than
  atoms.
• These charges are called electrons.

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8.1 Electric current

• Electric current is similar in some ways to a
  current of water.
• Like electric current, water current can carry
  energy and do work.
• A waterwheel turns when a current of water exerts
  a force on it.

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8.1 Electric current

• Electric current is what makes an electric motor
  turn or an electric stove heat up.
• Electric current is measured in amperes honor of
  Andre-Marie Ampere.

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8.1 Electric current

• Electric current can carry great deal of energy.
• An electric motor the size of a basketball can do
  as much work as five big horses or twenty strong
  people.

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8.1 Voltage

• When two containers of water are the same height,
  no water will flow.
• No current flows when there is zero voltage
  difference, which is why a dead battery wont
  light a bulb.

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8.1 Voltage

• Current flows from higher voltage to lower
  voltage.
• It is a difference in voltage that makes
  electrical current flow just as a difference in
  height makes water current flow.

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8.1 Batteries

• Since electric current in wires is invisible,
  think of a current of marchers, each carrying a
  bucket of energy.
• The battery refills the buckets with fresh energy
  and the bulb uses the energy to make light and
  heat.

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8.1 Batteries

• A pump is like a battery because it brings water
  from a position of low energy to high energy.

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8.1 Batteries

• A battery uses stored chemical energy to create
  the voltage difference.
• Three 1.5-volt batteries can be stacked to make a
  total voltage of 4.5 volts in a flashlight.