Lecture 19-Wednesday March 11 Magnetic Forces on Moving Charges Mass Spectrometers.
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Transcript of Lecture 19-Wednesday March 11 Magnetic Forces on Moving Charges Mass Spectrometers.
Lecture 19-Wednesday March 11
Magnetic Forces on Moving ChargesMass Spectrometers
Review of Monday
• Field of a long straight wire• Field of a loop• Field of a solenoid
Drawing Field Vectors and Field Lines of a Current-Carrying Wire
Slide 24-21
0( )2
IB r
r
Point P is 5 cm above the wire as you look straight down at it. In which direction is the magnetic field
at P?
A B C D E
20% 20% 20%20%20%
1. A2. B3. C4. D5. E
Checking Understanding
A. 10 A to the right.
B. 5 A to the right.
C. 2.5 A to the right.
D. 10 A to the left.
E. 5 A to the left.
F. 2.5 A to the left.
The magnetic field at point P is zero. What are the magnitude and direction of the current in the lower wire?
Slide 24-27
The Magnetic Field of a Current Loop
Slide 24-23
0
2CENTER OF LOOP
IB
R
The Magnetic Field of a Solenoid
A short solenoid A long solenoid
Slide 24-24
The Magnetic Field Inside a Solenoid
Magnetic field inside a solenoid of length L with N turns.
B0 IN
L
Slide 24-31
Quiz #7
• What is the magnetic field strength and direction at point A?
10 A
10 A
2 cm
2 cmA
The Force on a Charged Particle Moving in a Magnetic Field
Slide 24-32
The Right-Hand Rule for Forces
Slide 24-33
Slide 24-34
Paths of Charged Particles in Magnetic Fields
r mv
qB
Slide 24-35
Charged particle moving perpendicular to uniform magnetic field
• Magnetic force is perpendicular to velocity:
• What path if F ┴ v ?
sinmF qvB qvB
2
Circ
mvF q vB
rmv
rq B
The Mass Spectrometer
Slide 24-36
qBrm
v
Next Monday
• Read: 24: 6—Force on a current carrying wire• Problems: 24: CQ10, MC33, 22, 25, 26, 29, 31,
WB 24: 16-22