Ang speed what is the angular speed of the electron a

16. Ang Speed. What is the angular speed of the electron?
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Second Long Exam Second Semester, AY 2015–2016 Physics 72
A. 2 . 85 × 10
- 14
rad
/
s
B. 3 . 51 × 10
13
rad
/
s
C. 1 . 14 × 10
- 9
rad
/
s
D. 8 . 78 × 10
8
rad
/
s
E.
17. Bilis. If the electron follows a circular orbit with radius 5 cm , what is the speed v of the
electron?
For the next two items, consider a proton with initial velocity v
0
ˆ ı moving in a region with
uniform fields B = B
0
ˆ
k and E = E
0
ˆ
k .
18. True that. Which of the following is TRUE about the initial net force on the proton?
I. It is purely due to the magnetic field.
II. It has a component along the - y -direction.
III. It has a component along the + z -direction.
19. Trajectory. Which of the following is a possible trajectory of the proton?
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Second Long Exam Second Semester, AY 2015–2016 Physics 72
20. FL tower. Two straight, parallel wires 0 . 20 m apart carry currents in opposite directions as
shown. What is the force per unit length exerted on each wire?
A. 28 × 10
- 6
N
/
m
, attractive
B. 28 × 10
- 6
N
/
m
, repulsive
C. 28 π × 10
- 6
N
/
m
, attractive
D. 28 π × 10
- 6
N
/
m
, repulsive
E.
21. Coilbie Coillat. A tightly-wound circular coil with radius 4 m and 25 turns carries a current
of 2 A . What is the magnetic field along the coil’s axis at a distance of 3 m from its center?
For the next two items, consider a long cylindrical conductor with radius c and current density
J uniformly distributed over its cross-sectional area. Let r be an arbitrary distance from the
conductor’s axis.
22. Si Jc o si Jr? What is the magnetic field magnitude inside the conductor ( r < c )?
23. B vs. r. Which of the following gives the correct plot of the magnetic field magnitude B
as a function of r ?
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Second Long Exam Second Semester, AY 2015–2016 Physics 72
24. Moving Charge. Consider a point charge + q located at the origin and moving at a constant
velocity v = π
m
/
s
ˆ
k . At this instant, what is the magnetic field vector at (0 , 0 . 5 m , 0) ?
A. +
μ
o
q
16
ˆ ı
B. + μ
o
q ˆ ı
C. - μ
o
q ˆ ı
D. zero
E.
A – 8

Second Long Exam Second Semester, AY 2015–2016 Physics 72