Bellringer

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Bellringer

• How many kW are in 25000 watts?

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Electricity, Magnetism, and Motion

• Notes

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Electric Current and Magnetism

• Wherever there is electricity, there is
  magnetism.
• An electric current produces a magnetic field.
• This relationship between electricity and
  magnetism is known as electromagnetism.

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Solenoids

• The magnetic field produced by a current can
  change in 3 ways
• On/Off
• Direction
• Strength (add loops to the coil)

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Solenoids

• A coil of wire with a current is called a
  solenoid.

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Electromagnets

• A solenoid with a ferromagnetic core
  (Iron-magnet) is called an electromagnet.
• The overall magnetic field of an electromagnet
  can be hundreds or thousands of times stronger
  than the magnetic field produced by the current
  alone.
• An electromagnet is a strong magnet that can be
  turned on or off.

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Electrical Energy and Motion

• A magnet can move a wire with a current. The
  magnetic field of the magnet interacts with the
  magnetic field of the wire with a current. The
  result is that the wire moves.

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Electrical Energy and Motion

• The ability to move an object is called energy.
  The energy of electric currents is called
  electrical energy.
• The energy of motion is called mechanical energy.
  
• Electrical energy changes into mechanical energy
  when a wire with a current is placed in a
  magnetic field. The electrical energy produces
  the magnetic field in the wire with a current.
  The movement that results is mechanical energy.

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Galvanometers

• A galvanometer is a device that measures small
  currents.
• A galvanometer contains an electromagnet. The
  electromagnet is between the opposite poles of
  two permanent magnets.

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Galvanometers

• A current in the EM produces a magnetic field.
  The EMs magnetic field interacts with the
  magnetic fields of the permanent magnets. This
  interaction causes the EM to move.
• A pointer is attached to the EM in a
  galvanometer. When the EM moves, the pointer
  moves. A scale shows how much the pointer moves.
  The current through the EM is measured on the
  scale.

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Electric Motors

• An electric motor uses an electric current to
  turn an axle. The axle is a rod. For example, an
  electric motor turns the axle of a fan. The fan
  blades are connected to the turning axle.

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Electric Motors

• The name for the wire (or wire loops) that
  contains the current and rotates is known as the
  armature.

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Electric Motors
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Electric Motors

• An electric motor works by changing electrical
  energy into mechanical energy.
• In an electric motor, a loop of wire spins
  continuously. It spins continuously by changing
  the direction for the current at each half turn
  of the loop. Every half turn of the axle, the
  current reverses. First it goes one way, and then
  it goes the opposite way.
• The part of an electric motor that reverses the
  current is called a commutator. A commutator is a
  ring split in half.

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Electric Motors

• As the commutator rotates with the armature, it
  slides past two contact points called brushes.
  Each half of the commutator is connected to the
  current source by one of the brushes.
• As the armature rotates, each part of the
  commutator contacts one brush, then the other.
  Because the brushes conduct the current, changing
  brushes reverses the direction of the current in
  the armature.
• The reversing of the direction of the current
  causes the armature to spin continuously.

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