Q1: A uniform magnetic field is directed into the page. A Charged

```Phys102
Term: 131
Online HW-Ch28-Lec02
Q1:
A uniform magnetic field is directed into the page. A Charged particle, moving in the
plane of the page, follows a clockwise spiral of decreasing radius as shown. A
reasonable explanation is:
A.
B.
C.
D.
E.
the charge is positive and slowing down
the charge is negative and slowing down
the charge is positive and speeding up
the charge is negative and speeding up
none of the above
Ans:
B
Q2:
An proton with a velocity of v = − 3.0 &times; 105 ı̂ (m/s) enters a region of space where
there is a magnetic field given by B = − 5.0 &times; 10 − 4 ȷ̂ (T). What is the frequency
of revolution of the proton? (Give the answer in three significant figures and SI units)
Ans:
=
f
qB
5 &times;10−4 &times;1.6 &times;10−19
=
=
13.98 &times;106 Hz
−31
2π m
6.28 &times; 9.11&times;10
f = 14.0 MHz
Q3:
A long straight wire carries a 6.0-A current that is directed in the positive x direction.
When a uniform magnetic field is applied perpendicular to a 3.0-m segment of the
wire, the magnetic force on the segment is 0.36 N, directed in the negative y direction.
What is the magnetic field? (Give the answer in three significant figures and SI units)
Ans:
  
F= iL &times; B
F = iL &times; B &times; sin (θ)
=
B
Fmax 0.36
=
= 20.0 mT
i&times; L 6&times;3
KFUPM-Physics Department
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