THE uncovering of the theories behind a motor

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THE uncovering of the theories behind a motor
Department of Physics and Astronomy PHYS 420
Physics Demonstration

• University of British Columbia
• Presenter Eric Yeh

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What are we doing today?

• We are going to learn the basic functions,
  principles, and applications of an electric
  motor.
• We are also going to build a very simple motor
  today right here in this classroom.

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What is a Motor?

• Definition
• A rotating machine that converts electrical
  power (either alternating current or direct
  current) into mechanical power.
• Is this definition very satisfying?

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The Types of Motor

• DC (Direct Current) Motor
• AC (Alternating Current) Motor
• Linear Motor
• Stepping Motor
• Reluctance Motor
• The type of motor that we are going to see today
  is a type of DC motor.

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Linear Motor

• A few countries are using powerful electromagnets
  to develop high-speed trains, called maglev
  trains.
• Maglev is short for magnetic levitation, which
  means that these trains will float over a guide
  way using the basic principles of magnets.

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How Does A Motor Do Work?

• There are couple main principles behind a working
  DC Motor.
• In simple terms, they are
• Amperes Law
• Right Hand Rule
• The Magnetic Field Force
• Torque Power

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How Does A Motor Do Work?
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The Electromagnet

• Electromagnets are usually in the form of iron
  core solenoids.
• The iron nails line up with the smaller driving
  magnetic field produced by the current in the
  solenoid.
• This multiplies the magnetic field by factors of
  tens to even thousands.
• The solenoid field relationship is
• k is the relative permeability of the iron, shows
  the magnifying effect of the iron core. µ0 is the
  permeability of the air.

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The Electromagnet
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The Electromagnet
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The Magnetic Field
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The Current
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The Current
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The Force
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Theory Behind a Working Motor
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The Torque
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Our Demonstration today
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The Motor that We are Building

• Materials Required
• One 'D' Cell Alkaline Battery
• 2 Pieces of Aluminum Tape
• Two Large Paper Clips
• One Rectangular Ceramic Magnet
• Heavy Gauge Magnet Wire (the kind with red enamel
  insulation, not plastic coated)
• Fine Sandpaper
• Optional Glue, Small Block of Wood for Base

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The Motor that We are Building
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The Motor that We are Building

• On one tail, use fine sandpaper to completely
  remove the insulation from the wire.
• Leave about 0.5 cm of insulation on the end where
  the wire meets to coil. On the other tail, lay
  the coil down flat and lightly sand off the
  insulation from the top half of the wire only.
• Again, leave 0.5 cm of full insulation on the end
  and where the wire meets the coil.

• Starting about 8 cm from the end of the wire,
  wrap it 7 times around the battery provided.
• Cut the wire, leaving a 8 cm tail opposite the
  original starting point.
• Wrap the two tails around the coil so that the
  coil is held together and the two tails extend
  perpendicular to the coil.

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The Motor that We are Building

• Bend the two paper clips into the following shape
  
• Use the aluminum tape to hold the loop ends to
  the terminals of the "D" Cell battery
• Stick the ceramic magnet on the side of the
  battery as shown

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The Motor that We are Building

• Place the coil in the cradle formed by the right
  ends of the paper clips.
• You may have to give it a gentle push to get it
  started, but it should begin to spin rapidly.
• If it doesn't spin, check to make sure that all
  of the insulation has been removed from the wire
  ends.

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The Applications of a Motor
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What about a Generator

• The current running through coils of wire would
  produce magnetic field that attracts or opposes
  the existing permanent magnet, which then drives
  the coil of wire to move or rotate.
• Reversely, coils of wire moves or rotates in a
  magnetic field would also produce a current.
  This is what a generate does.

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How Does a Generator Work
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A Simple Generator Demo
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A Simple Generator Demo
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A Simple Generator Demo

• We are going to try to rotate the center rod to
  create current with the effect of the magnetic
  field
• When we rotate the rod, we will use a voltmeter
  to test whether or not the current is produced.
• Also, the positive and negative current reading
  depends on the direction of the spin.

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Types of Generator?

• SYNCHRONOUS GENERATORS
• Synchronous generators are most often used for
  "emergency" or "standby" power, but in many cases
  may be used to provide all of the power
  requirements of a facility.
• INDUCTION GENERATORS
• Induction generators are most often used for
  "peak shaving" (providing the power needed for
  starting large motors, additional air
  conditioning load on hot days, etc.)

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How can Motors and Generators help us?

• With the theory of conservation of energy, we
  know that the energy will not disappear. Rather,
  energy would change from one form to another. In
  our discussion today, we have seen electrical
  energy turn into mechanical energy and also from
  mechanical to electrical.
• Motors would help us to utilize the electrical
  energy that we have to do work through the form
  of mechanical energy.
• Generator does the opposite. It transforms
  mechanical energy into electrical energy.
• Generator is able to provide us with the source
  of electricity when we provide other forms of
  energy or materials that could react to release
  energy.

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A Better Definition

• Electric motors involve moving or rotating coils
  of wire which are driven by electric current
  producing magnetic force that opposes the
  magnetic field. They transform electrical energy
  into mechanical energy.