Transcript Document
Magnetic Force on a Charged Particle 1 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 2 3 4 5 6 7 8 9 10 11 12 20-3 Force on Electric Current in Magnetic Field 13 No force, vectors are parallel F = qvB = (3.0x10-6C)(3x105m/s)(200x10-3 T) F = 1.8x10-1 N down 14 F = qVB sin q direction: up 15 Motion of Charged Particles in a Magnetic Field 16 17 18 +q is forced down toward the bottom of the page 19 • F = qvB • B = F/qv = 2000N • C(1.6x10 -19C)(3x105 m/s) • B = _____T 20 F = qVB = (1.60x10-19 C) (300,000 m/s) (2000x10-3 T) Direction: out of the page 21 F = Eq = 2000 N/c (1.60 x 10-19 c) = Direction: out of page (use left hand for electron) 22 F = qVB = 1.60 x 10 -19 c (300,000 m/s)(2 T) = Direction: down 23 Magnetic Force on Current Carrying Wires 24 B = F/qV = 400V/20,000 m/s = A volt is work done per unit charge (J/q) Direction: into the page 25 F = I L B sin Q F = (30A)(100m)(0.4T)(sin90) F = _____________N 26 F = I L B B = F / I L = (40N/m) / 15A = Current moving to the right 27 Sources of Magnetic Fields 28 29 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 30 31 32 33 34 35 36 r2 r1 Opposite I1 = 10.0 A 7.0 m Directions could be zero I2 = 13.0 A 37 38 39 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 40 I B A B - out A - in 41 42 Magnetic Flux 43 44 45 46 47 a) 0 b) Max: F = BAcos q = 4.2x10-3T(6m2)cosq = ___ Weber c) F = BAcos q = 4.2x10-3T(6m2)cos30 = ___ Wb 48 F = B p r2 cos 40 r = sr [F / B p cos 40] r = sr [.250Wb / (0.050T)(3.14)(cos40) = ______m 49 50 •http://hyperphysics.phyastr.gsu.edu/hbase/electric/farlaw.html 51 E = - 1000 (500 x 10-3 T / 0.01 s) = ___V 52 53 •http://www.launc.tased.edu.au/online/sciences/phy sics/Lenz's.html 54 55 56 clockwise 57 counterclockwise 58 59 60 B = mo I / 2 p r I = 2 p Br / mo = mo = 2 p x 10-7 Power = I2 r = 61 Direction of current through 3 ohm resistor is down 62 63 64