Download Lecture 26

Agenda
• This Week
– Ch. 27-29
– Skip Lab, No Quiz
• Next Week
– Finish 29, No Quiz
– Review
• Following
– Exam II on Monday (2 weeks)
– April 6th [Or previous Friday if prefer]
• Sections
– 27.1-27.8
– 28.1-28.5
– 29.1-29.5
Magnetism
• Much like electric Dipole
• Combination of
– North (+)
– & South (-)
• ALWAYS BOTH
Magnetism
• Lines Originate at N
• Lines End at S
N
– More Common than E Fields
– Why?
S
Fields & Forces
• E & B (Magnetic) Fields
– Same
– Fields create forces
– B & E Fields act on charged particles
• Different?
– B fields act on MOVING charges
– E fields act in straight lines
– B Fields act in perpendicular directions
Right Hand Rule
Directions for + Charge in B Field
Same Idea as Rotational Motion
Negative Charge = Opposite Direction
“Left Hand” rule for electrons?
Be consistent
Or.. F = qvBsin(q), Use R.H.R. for directions
Trial 1
+
B Field Points Right
What is the trajectory for this particle?
Positive Charge, Constant Velocity to the Right…
Trial 2
X
X
X
X
X
X
X
X
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X
X
X X
X
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+
X
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X
B Field Points Into Screen
What is the trajectory for this particle?
Positive Charge, Constant Velocity Right?
Initial: Force points ? …
Down
X
X
X
X
X
X
X
Trial 2
X
X
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X
X
X
X
X
X
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X X
X
X
X
+
X
X
X
X
X
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X
B Field Points Into Screen
What is the trajectory for this particle?
Positive Charge, Constant Velocity Right?
Curves Around, now Velocity is Down
Force Points?
Left…
X
X
X
X
X
X
X
X
X
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X
Trial 2
X
X
X
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X
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X X
X
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+
X
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X
Vo
X
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X
X
Velocity, Force & Field Always Perpendicular
When Force always points inwards… Circular Motion
X
X
Trial 3
+
B Field Points Right
What is the trajectory for this particle?
Positive Charge, Constant Velocity Up & Right…
To Solve, Separate out x & y components, treat separately
Trial 3a
+
Just Like First Part:
B Field Points Right
What is the trajectory for this particle?
Positive Charge, Constant Velocity to the Right…
Trial 3b
+
Just Like 2nd Part:
B Field Points Right
Charge will make circle in yz plane
Trial 3
+
X part: + Charge travels to right
Y Part: Circle in yz plane
Combined: Helix: Oscillating circle traveling to right
Only 3 choices: Circle, Line, Helix
Trial 4
A wire is located in a field with B pointing right.
Current in the wire flows upwards
Is there a force on the wire, if so which direction?
Break
• HMWK Assistance?
• Tomorrow
– Finish 27 – Mathematical Problems
• Wed & Fri
– Finish 28, Begin 29
• Monday& Tues
– Finish 29, Problems
• Wed
– Review
• Fri
– Exam