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971-Motor Behaviour

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971-Motor Behaviour
Teacher notes - Prior knowledge
• Describe the shape of a field around a straight wire,
solenoid
• Describe that a current carrying wire at right angles to a
magnetic field experiences a force
• Use Fleming’s left hand rule to predict the direction of a
force on a current carrying conductor
• Use the right hand rule to predict the direction of field
around a current carrying conductor
motors
P2
Success Criteria
• Build a simple dc motor
• Use Fleming’s left hand rule to explain
how your motor spins
• Use the idea of combining fields to explain
how your motor spins
1 Minute Presentation
(Mr)
(Fleming’s)
(Cat)
Teacher notes
• Provide class with a selection of motors
collected from old / broken household
items (eg. hairdryer, food mixer, tape
recorder, video player, drill etc.)
Thinking about motors
• What do they have in common?
• How do you think they work?
• Where do you think they are
used?
Teacher notes
• Can demo ‘paper clip motor’, ‘screw motor’
and or ‘spiral motor’. Several other
examples on you tube
http://www.youtube.com/watch?v=UhMkUOWaN3M
Teacher notes
• Introduce the motor kit apparatus.
• Take pupil suggestions as to how to
constuct.
• Pupil activity: Build motors
• 2 challenges with appropriate
help/explanations follow
25-Mar-16
25-Mar-16
CHALLENGE
• Use Fleming’s LEFT hand rule to explain how
your motor works.
Motion
(Mr)
Field
(Fleming’s)
(cat)
N
S
N
= current out of page
= current into page
S
N
S
http://www.youtube.com/watch?v=FjNnRyLexNM
CHALLENGE
• Draw fields around the wires and between the magnets.
• How do they combine to make your motor spin?
Direction of
current
N
Direction of
field
S
extension
The right hand rule
• You can work out the
direction of the field using
your right clenched fist.
Direction of
current
• Reversing the direction of
the current
will reverse the magnetic
field direction.
Direction of
field
Forces caused by fields
SOUTH
DECREASED
FIELD
INCREASED
FIELD
MOTION
NORTH
N
Field
reduced
S
Field
increased
Use key ideas from today’s lesson
to annotate your diagram
Homework activity
• What is a split ring commutator?
• Why do practical motors have
curved pole pieces?
Fly UP