Physics 112 HW17
Due Wednesday, 29 October 2014
/5
QVB02. A particle with mass 1.81 g and a charge of 12.2 nC has, at a given instant, a velocity v
= (30,000 m/s)ĵ. What are the magnitude and direction of the particle’s acceleration produced
by a uniform magnetic field B = (1.63 T)î + (0.980 T)ĵ?
QVB03. An electron moves at 2,500,000 m/s through a region in which there is a magnetic field
of unspecified direction and magnitude 0.0740 T.
a) What are the largest and smallest possible magnitudes of the acceleration of the electron
due to the magnetic field?
b) If the actual acceleration of the electron is ¼ of the largest magnitude in part a), what is
the angle between the electron velocity and the magnetic field?
QVB04. An electron at point A in the diagram at right has a
speed vo of 1,410,000 m/s.
a) Find the magnitude and direction of the magnetic field
that will cause the electron to follow the semicircular
path from A to B.
b) Find the time required for the electron to move from A
to B.
QVB05. In an experiment with cosmic rays, a vertical beam of
particles that have charge of magnitude 3e (e is the charge of a
single proton) and mass 12 times the proton mass enters a
uniform horizontal magnetic field of 0.250 T and is bent in a
semicircle of diameter 95.0 cm, as shown in the figure at right.
a) Find the speed of the particles and the sign of their charge.
b) Is it reasonable to ignore the gravity force on the particles?
c) How does the speed of the particles as they enter the field
compare to their speed as they exit the field?
vo
A
-
B
10.0 cm
95.0 cm
QVB06. (Toughie!) A velocity selector consists of perpendicular
+ q
electric and magnetic fields as shown in the diagram at right.
v
a) What strength magnetic field is needed so that only ions of
    
speed 2000 km/s will emerge undeflected, if the electric field
    
is 200,000 N/C? Will positive ions be separated from
negative ions?
    
b) In a certain velocity selector, the electric field is produced by
    
a variable-voltage battery connected across large, parallel,
metal plates that are separated by 3.25 cm, and the magnetic B   E  
field comes from an electromagnet whose field strength can
be varied. If the battery voltage can range between 120 V and
560 V and the magnetic field between 0.054 T and 0.180 T, what range of ion velocities
can this selector be adjusted to produce?
B