foundations of physical science workshop: electric motor
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Foundations of Physical Science
Workshop: Electric Motor
Electric MotorCPO Science
Key QuestionsHow are electricity and magnetism related?
How does an electric motor work?
OverviewM a g n e ts
B u i l d a n E l e c t r i cM o to r
D e s i g n a n d B u i l dD i ff e r e n t M o to r s
Fun with MagnetsTake your motor completely
apart to expose the little ceramic magnets that are in the rotor pockets
What “stupid magnet tricks” can you come up with?
Compare force of attraction with force of repulsion
Fun with Magnets
100 20 30 40 50 60 70 80 90 100 110 120 130 140D istance in m illim eters
AttractRepel
AttractRepel
AttractRepel
distance
N-S S-S N-N
Distance 1
D istance 2
D istance 3
Slide the second m agnetcloser and closer untilthe first one m oves.
F irst m agnet
Second m agnet
S - S R e p e l
N - N R e p e l
S - N A t t r a c t
How does a motor work?
A t t r a c t
R e p e l
R o to r
M a g n e ts o n th e o u ts i d e ( s ta to r )p u s h a n d p u l l o n m a g n e ts o n th ei n s i d e ( r o to r )
ElectromagnetsCoil of wire wrapped around a steel pin
You can reverse polarity by switching direction of electricity
Electromagnets
N
N
E l e c t r i cC u r r e n t
E l e c t r i cC u r r e n t
E l e c t r o m a g n e t M o d u l e
C o i l o f W i r e
T h i ck S te e l P i n
E l e c t r i c E y e
Switching electromagnet polarityMechanism that makes electric current switch direction is called a commutator
Clear = north
Black = south
Switching electromagnet polarity
N
N
A
A
B
B
C
C
S w i tch
Rota
t i on
C l e a r = n o r th p o l e
B l a ck = s o u th p o l e
Build a 4-pole electric motor
4 a l te r n a t i n g m a g n e ts
p i n k d i s c
co n n e c t b a t te r y p a ck
h o l d th e r u n b u t to n
n u d g e to s ta r t
Design other motors Using other colored disks, decide
how to build a working motor
Save the green disk for last – it’s a bit tricky!
Use a photogate to measure frequency, and from that calculate the speed in rev per sec (frequency divided by # black areas)
Who can build the fastest motor?
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