Electricity and Magnetism E

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Review
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It looks like a solenoid, it acts like a
solenoid--why?
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It looks like a solenoid, it acts like a
solenoid--why?
Cross section of magnetized iron
magnetization current
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It looks like a solenoid, it acts like a
solenoid--why?
Cross section of magnetized iron
But why are they all lined up in the first place?
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Torque (i.e., twisting force) on a current
carrying loop.
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Torque (i.e., twisting force) on a current
carrying loop.
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Torque (i.e., twisting force) on a current
carrying loop.
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Electro-magnet

• Amplifier of the field due to a current loop.

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Electro-magnet

• Amplifier of the field due to a current loop.

remove the loop
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Electro-magnet

• Amplifier of the field due to a current loop.

hard
soft
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Keeping it all straight...

• Three ways to set up a magnetic field
• Bar magnet
• Solenoid
• Straight wire
• Four ways objects are pushed by a field
• Charge moving in a field
• Current in a field
• Bar magnet (solenoid) in uniform field
• Bar magnet (solenoid) in non-uniform field

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Why is there a solenoid on your starting motor?
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Why is there a solenoid on your starting motor?

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Why is there a solenoid on your starting motor?

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What is the direction of the force on the right
loop?
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What is the direction of the force on the right
loop?
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What is the direction of the force on the right
loop?
N
S
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TOP VIEW
Will the magnet pivot clockwise or
counterclockwise?
N
S
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TOP VIEW
Will the magnet pivot clockwise or
counterclockwise?
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Electric Motor
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Electric Motor
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Electric Motor
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Electric Motor
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Electric Motor
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Electric Motor
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Electric Motor
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Electric Motor
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Electric Motor
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Electric Motor
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Electric Motor
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An electron is injected between two charged
plates as shown. The B field is fixed and the
charge on the plates is adjusted until the
electron passes undeflected. Which plate is
positive and which is negative?
-Q
B
e
-Q
What is the net force on the electron?
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What direction is the magnetic force?
What direction is the electric force?
What direction do the electric field lines point?
Which plate is positive?
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If the electron slowed down, would the electron
veer high or veer low?
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If the electron slowed down, would the electron
veer high or veer low?
FB