1 magnetic force on a charged particle. 2 chapter assignments chapter 20 hw#1 q2,3,9-11 and p1,7,8,...

1

Magnetic Force on a Charged Particle

2

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

3

4

5

6

7

8

9

10

11

12

13

20-3 Force on Electric Current in Magnetic Field

14

F = qvB = (3.0x10-6C)(3x105m/s)(200x10-3 T)

F = 1.8x10-1 N down

No force, vectors are parallel

15

F = qVB sin direction: up

16

Motion of Charged Particles in a Magnetic Field

17

18

19

+q is forced down toward the bottom of the page

20

• F = qvB• B = F/qv = 2000N• C(1.6x10 -19C)(3x105 m/s)• B = _____T

21

F = qVB = (1.60x10-19 C) (300,000 m/s) (2000x10-3 T)

Direction: out of the page

22

F = Eq = 2000 N/c (1.60 x 10-19 c) =

Direction: out of page (use left hand for electron)

23

F = qVB = 1.60 x 10 -19 c (300,000 m/s)(2 T) =

Direction: down

24

Magnetic Force on Current Carrying Wires

25

B = F/qV = 400V/20,000 m/s =

A volt is work done per unit charge (J/q)

Direction: into the page

26

F = I L B sin

F = (30A)(100m)(0.4T)(sin90)

F = _____________N

27

F = I L B B = F / I L = (40N/m) / 15A =

Current moving to the right

28

Sources of Magnetic Fields

29

30

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

31

32

33

34

35

36

37

I1 = 10.0 A

I2 = 13.0 A

7.0 m

r2 r 1

Opposite

Directions could be zero

38

39

40

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

41

B

A

B - out

A - in

42

43

Magnetic Flux

44

45

46

47

48

a) 0

b) Max: = BAcos = 4.2x10-3T(6m2)cos = ___ Weber

c = BAcos = 4.2x10-3T(6m2)cos30 = ___ Wb

49

F = B r2 cos 40

r = sr [ / B cos 40]

r = sr [.250Wb / (0.050T)(3.14)(cos40) = ______m

50

51

•http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html

52

E = - 1000 (500 x 10-3 T / 0.01 s) = ___V

53

54

•http://www.launc.tased.edu.au/online/sciences/physics/Lenz's.html

55

56

57

clockwise

58

counterclockwise

59

60

61

B = o I / 2 r I = 2 Br / o =

= 2 x 10-7

Power = I2 r =

62

Direction of current through 3 ohm resistor is down

63

64