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Magnetic Force and Motors. Physics 12. Joke of the day:. Special song clip of the day:. Featuring Canadian ISS commander: Chris Hadfield! http://www.wimp.com/singscollaboration/. Review:. page 767 # 1, 2 Remember RHR#1 - PowerPoint PPT Presentation
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MAGNETIC FORCE AND MOTORSPhysics 12
Special song clip of the day:
Featuring Canadian ISS commander: Chris Hadfield!
http://www.wimp.com/singscollaboration/
Review:
page 767 # 1, 2
Remember RHR#1 Thumb of your right hand pointing in the
direction current and your fingers will wrap around the conductor in the direction of the induced magnetic field.
1 (a)
Current Coming Towards You
Current Moving Away From You
X
1 (b): note how the two magnetic fields combine to create one big loop on the outside
Both currents flowing towards viewer
1(c):
X
North
South
One current towards viewer and other current going away from viewer
RHR#2
Solenoids
Loops of Wire:
If the wire is shaped into a single loop, using RHR1, the behaviour of the magnetic field can be visualized
Solenoid:
If the wire is formed into many loops, a solenoid is created
And if we wrap a wire into several coils (and usually around a soft iron core) we create a solenoid that is also an electromagnet
Advantages of electromagnets: The strength of an electromagnet can easily be
changed by changing the amount of electric current that flows through it.
The poles of an electromagnet can even be reversed by reversing the flow of electricity.
Right Hand Rule #2:
Gives the direction of the North Pole in a solenoid Fingers curl in direction of current Thumb points to N pole
Force Experienced by Charged Particle in a Magnetic Field
Review: What is current?
I = q_ Δt It is a flow of electric charge. Is carried by moving electrons in a wire!
Hmmmm….moving electrons….so they have velocity!
What does this remind you of? Pipe cleaner time again! X represents magnetic
field into the board Let’s think about
directions: Velocity initially is….
To the right Field into the board What direction does the
force have to be acting in? Up or down
Oh no we’re in 3D now!
Charged Particle in Magnetic Field: The force acting on the charged particle is
proportional to speed and charge Magnitude and direction of force depend
on velocity of particle as well as magnitude and direction of magnetic field
When particle moves parallel to field, zero force experienced
Force acts perpendicularly to both velocity and field
RHR #3/ LHR#3:
Use to determine the direction of the force when the current and magnetic field are known
Thumb = force Index = magnetic field Middle = current
Right vs Left:
Use right hand if positive charge and left hand if negative charge
LeftRight
Video clip:
http://www.youtube.com/watch?v=HTTA30sEv6o
Practise:
Try it :
Practise sheet Work on lab