BabyQuiz

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Baby-Quiz

• Which of the following affects the resistance of
  a wire diameter, type of material, length, or
  temperature? Explain.
• Which circuit offers the greater resistance to to
  battery, two bulbs in series or two bulbs in
  parallel? Why?
• If a string of five bulbs in series is added in
  parallel to a single-bulb circuit, you find that
  the brightness of the original bulb does not
  change. Has the current through the battery
  increased, decreased, or stayed the same? Has the
  resistance of the circuit increased, decreased,
  or stayed the same? Explain.
• What happens to the power supplied to a battery
  if the resistance connected to the battery is
  doubled? Why/

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Magnets and Magnetic Fields
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Important do not confuse the magnetic poles and
electric charges!
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If a bar magnet is broken into two pieces, how
many magnetic poles are there?
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Magnetic Field Lines
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Source of Magnetism
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Electric current produces a magnetic field!!!
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Direction of Magnetic Field Produced by a
Current-Carrying Wire Right-Hand Rule
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Grasp the wire with your right hand so that your
thumb points in the direction of the conventional
(positive) current then your fingers will
encircle the wire in the direction of the
magnetic field.
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Force on an Electric Current in a Magnetic Field.
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Important the direction of the force is always
perpendicular to the direction of the current and
also perpendicular to the direction of the
magnetic field.
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Another Right-Hand Rule(for the Force)
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Force on Electric Current in a Magnetic Field
Maximum FIlB
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Units of Magnetic Field
1 Tesla (T) 1 N/A m 1 Gauss (G) 10-4 T
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Force on an Electric Charge Moving in a Magnetic
Field
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Maximum FqvB
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Right-Hand Rule Again
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Important right-hand rule defines direction of a
force acting on a positive charge. For negatively
charged particles the force is in exactly the
opposite direction. Dont forget this when you
are answering questions about electrons!!!
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Protons Path in a Uniform Magnetic Field
A proton travels at velocity v in a plane
perpendicular to a magnetic field. Describe its
path.
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Conceptual Example A Spiral Path
What is the path of a charged particle if its
velocity is not perpendicular to the magnetic
field?
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Magnetic Field Due to a Straight Wire
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Magnetic Field of a Solenoid
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When you look down the axis of a solenoid so that
the current circulates in the counterclockwise
direction, are you looking in the direction of
the magnetic field or opposite of it? Explain.
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Force between Two Parallel Wires
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Each current produces magnetic field that is
felt by the other wire so that each must exert
a force on the other.
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Parallel current in the same directions attract
each other, antiparallel currents repel.
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Parallel current in the same directions attract
each other, antiparallel currents repel.
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An electric circuit and telephone lines. Two
wires carrying currents in opposite direction are
twisted together. How does this reduce the
magnetic fields surrounding the wire?