1. Announcement Exam #1 grades are posted on E-learning
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Master copy of exam #1 (correct answer 1) posted on E-learning

2. Magnetic field (strength) Length of the section in B-field
Magnetic induction
Magnetic flux density
Magnetic field (strength)
[B] = [F/IL]
= Ns/Cm = Tesla
*1 Tesla = 104 gauss
FB = ILB
Length of the section in B-field

3.  FB = IL(Bsin) B B FB = ILB┴ I A net force on the loop
A net torque on the loop
A net force and torque
nothing, zip

4. X X S N

6. DC Electrical Motor X X X X X X X X X

7. Example
The earth’s magnetic field in Colorado is 0.59 G. It is directed at an angle of 67° below horizontal. Find the force on 5.0 m of an east-west wire carrying a westward current of 20 A. North-South wire?

8. Are there ghosts in town?
In Colorado,
B = 0.59 G = 5.9 x 10-5 T X
67 degree F
S N
Are there ghosts in town?
Force on a 5 m E-W wire carrying a 20 A west-bound current? N S
F = ILB
= (20 A)(5 m)(5.9x10-5 T)
= 5.9 x 10-3 N X

9. FB = ILBsin on a wire FB = qvBsin on a charge- F
F = I L B┴
dF = I (dL) B
= (dQ/dt) dL B
= dQ (dL/dt) B
= dQ v B F dF dL
F = Q v B
force on a moving charge
Lorentz force

10. Finding the Direction of Magnetic Force
The direction of the magnetic force is always perpendicular to both v and B
F = qvB sin
Fmax occurs when v is perpendicular to B
F = 0 when v is parallel to B

11. Right Hand Rule Hold your right hand open
Place your fingers in the direction of B
Place your thumb in the direction of v
The direction of the force on a positive charge is directed out of your palm
If the charge is negative, the force is opposite that determined by the right hand rule

12. My Old TV

13. Nam June Paik

14. Force by a magnetic field on a moving charge is always q v F q v F
X x x x x q v F F v q v F q
F = q v B┴
Force by a magnetic field on a moving charge is always
Perpendicular to the direction of motion.
NO WORK DONE BY THE FIELD!!!

15. This force causes a circular motion. Centrepetal force = FB
X x x x x B r v
FB = q v B
Force by B-field q m
This force causes a circular motion.
Centrepetal force = FB
Fc = mv2/r = q v B = FB
r = mv/qB
Since there is no work done by the field, in vacuum,
The charge will make a circular motion forever!!!

16. Bubble Chamber

17. An object with +e charge
B = 0.36 T
r = 0.4 m
An object with +e charge
And mass m kg
A univalent ion with mass m
Came into the field region with
Speed v = 6 x 105 m/s.
Mass m?
Mass spectrometer