Right Hand Thumb Rule 3

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Right Hand Thumb Rule 3

• 16.2

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Quick Review

• 1) How is a solenoid like a bar magnet?
• 2) Draw a diagram using correct symbols showing
  a current carrying wire going into the page and
  the magnetic field it creates.
• 3) How could you make a solenoids magnetic
  field stronger?

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• 4) Draw the magnetic field and poles for this
  solenoid.

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• 5. If you grasp a solenoid with your right hand
  such that your fingers are in the direction of
  current flow in the wires, and extend your thumb
  at right angles to the plane of the coil,
• a. Your thumb will indicate which end of the
  solenoid is the south end.
• b. Your thumb will point opposite to the
  direction of the magnetic field inside the
  solenoid
• c. Your thumb will point in the direction of the
  magnetic field inside the solenoid
• d. The back of your hand will indicate the north
  end of the solenoid

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What happens when you have 2 interacting magnetic
fields?
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Force on a Wire

• A wire's magnetic field will interact with
  another external magnetic field, possibly
  experiencing a force depending on its orientation

• Where the current (I) in the wire is in amperes,
  the length (l) of the wire is in metres, B is the
  strength of the magnetic field in tesla (T), and
  ? is the angle between the wire and the magnetic
  field.
• If the wire is parallel to the magnetic field
  then there is no force on the wire

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Third Right Hand Thumb Rule (palm rule)

• hold your hand flat with your four fingers
  together and your thumb perpendicular to your
  fingers
• point your thumb in the direction of the positive
  current (I)
• extend your fingers straight out in the direction
  of the external magnetic field (B)
• your palm will then point in the direction of the
  force on the wire (F).

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Example 1

• A 3.2 cm wire is carrying a 34 mA current as
  shown in the magnetic field below that is
  directed to the right. The strength of the
  magnetic field is 0.23 T. Find the force
  (magnitude and direction) on the wire.

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Solution

• The magnetic field is to the right, and a
  component of the current is up the page. Using
  the third right hand rule,
• Fingers point to the right (with the magnetic
  field)
• Thumb points up the page
• Palm is left facing into the page
• The force is therefore into the page.

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Example 2
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(No Transcript)
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Example 3
Find the direction of the current flow.
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DOWN!
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Think about it

• Two wires with current flowing from left to write
  are parallel. Draw a diagram and prove if they
  are attracting or repelling each other?

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Motors

• A motor is a device that will convert electrical
  energy into motion
• This is possible because when an electric current
  occurs in a magnetic field, the induced magnetic
  field in the wire will interact with the magnetic
  field
• This will result in a force on the wire which can
  be determined using Right Hand Rule 3

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The Ampere

• Ampere theorized that the magnetic fields between
  two charge carrying wires would either result in
  attractive or repulsive forces
• Based on this, Ampere was able to develop an
  equation to describe the magnetic field