1 magnetic force on a charged particle. 2 chapter assignments chapter 20 hw#1 q2,3,9-11 and p1,7,8,...
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Magnetic Force on a Charged Particle
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Chapter Assignments
• Chapter 20• HW#1 Q2,3,9-11 and P1,7,8,• HW#2 P11(c), 12-14,17(c), 26,29,30(c) ,
48(c) and 49(c)• Chapter 21• HW#3 Q2,4,6,8 and P1-5,9(c),10(c),14,15
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20-3 Force on Electric Current in Magnetic Field
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F = qvB = (3.0x10-6C)(3x105m/s)(200x10-3 T)
F = 1.8x10-1 N down
No force, vectors are parallel
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F = qVB sin direction: up
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Motion of Charged Particles in a Magnetic Field
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+q is forced down toward the bottom of the page
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• F = qvB• B = F/qv = 2000N• C(1.6x10 -19C)(3x105 m/s)• B = _____T
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F = qVB = (1.60x10-19 C) (300,000 m/s) (2000x10-3 T)
Direction: out of the page
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F = Eq = 2000 N/c (1.60 x 10-19 c) =
Direction: out of page (use left hand for electron)
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F = qVB = 1.60 x 10 -19 c (300,000 m/s)(2 T) =
Direction: down
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Magnetic Force on Current Carrying Wires
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B = F/qV = 400V/20,000 m/s =
A volt is work done per unit charge (J/q)
Direction: into the page
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F = I L B sin
F = (30A)(100m)(0.4T)(sin90)
F = _____________N
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F = I L B B = F / I L = (40N/m) / 15A =
Current moving to the right
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Sources of Magnetic Fields
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Hand rules
• When current flows through a wire, it generates a magnetic field around the wire.
• The direction of the field is determined with one of the hand rules
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I1 = 10.0 A
I2 = 13.0 A
7.0 m
r2 r 1
Opposite
Directions could be zero
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How do we determine which way is north?
• When current is flowing through a coil, the coil acts like a bar magnet.
• We can predict which way is north using another rule
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B
A
B - out
A - in
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Magnetic Flux
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a) 0
b) Max: = BAcos = 4.2x10-3T(6m2)cos = ___ Weber
c = BAcos = 4.2x10-3T(6m2)cos30 = ___ Wb
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F = B r2 cos 40
r = sr [ / B cos 40]
r = sr [.250Wb / (0.050T)(3.14)(cos40) = ______m
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•http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html
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E = - 1000 (500 x 10-3 T / 0.01 s) = ___V
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•http://www.launc.tased.edu.au/online/sciences/physics/Lenz's.html
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clockwise
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counterclockwise
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B = o I / 2 r I = 2 Br / o =
= 2 x 10-7
Power = I2 r =
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Direction of current through 3 ohm resistor is down
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