PROBLEMS
451
2—6. A eld of 25 oersteds is applied perpendicularly to a cathode ray
whose electrons have a velocity of
1.88 X 109 cm. per sec.
What Wii]
be the rad1us of the c1rcle into Which they will be bent?
(4.25 cm.)
2—7. What voltage is_ needed to
return the spot of light in Thomson’s
e/m experiment to 1tsorrgrnal posrtion if the magnetic eld is of strength
30 oersteds, the veloc1ty of the electrons 2.66 >< 109 cm. per sec. and the
plates 1 cm. apart?
(798 Ua[ts)
2—8. In a Kirchner e/m experiment, when only one spot is observed,
the acceleratrng voltage
is 300 volts and the distance between the condens—
.
ers
is
50 cm.
Usrng e/m = 1.76 X 107 e.m.u./g., nd the frequency of
the oscillator.
2—9. The cathode ray tube used in the measurement of e/m by the
“
helical ” method has X and Y deection plates at distances from the
screen
of 14 and 16 cm., respectively. Measurements are to be made
over
a
range of magnetic eld values which will produce one, two, and
three spirals with the X plates, and over a corresponding range with the
Y plates.
The accelerating potential will be held constant at 1000 volts.
What is the largest magnetic eld which will be required?
2—10. From the relation,
77752, calculate (a) the energy corresponding to the mass of one electron, (b) the energy corresponding to
one mass-unit and (c) the energy corresponding to one millimass-unit.
2—11. How many
electron volts are needed to accelerate (a) a proton,
(à) an (gg-particle, to the same velocity as that of an electron accelerated by
one electron volt?
2—12. An electron is accelerated by 17 volts and bent into a circular
path of radins r cm. by a magnetic eld of strength H oersteds. Show
that Hr = 3.37x/77.
2—13. One ampere
is passed through a single turn of wire of radins
13 cm.
Compute the eld intensity at a point
cm.
or the ax1s and
3 cm. out from the center of the coil.
Compare With tl1epntensrty
on the
'
'
t
t
nd at the center of the cor .
ax1s at the same clis ance ou a
0.056, 0.048 oersted)
2—14. Compute the mass of an electron and of the hydrogen
ion in
solution.
_
2—15. Calculate the force on the plate
of a two-electrode tube when
bombarded by electrons accelerated by 200 volts, the plate
being
6 milliamperes and g/m : 1,77 >< 107 e.m.u./gram,
assumrng
a)
of their momentum is given up
when they strike the plate.
(0.0
y£
451
2—6. A eld of 25 oersteds is applied perpendicularly to a cathode ray
whose electrons have a velocity of
1.88 X 109 cm. per sec.
What Wii]
be the rad1us of the c1rcle into Which they will be bent?
(4.25 cm.)
2—7. What voltage is_ needed to
return the spot of light in Thomson’s
e/m experiment to 1tsorrgrnal posrtion if the magnetic eld is of strength
30 oersteds, the veloc1ty of the electrons 2.66 >< 109 cm. per sec. and the
plates 1 cm. apart?
(798 Ua[ts)
2—8. In a Kirchner e/m experiment, when only one spot is observed,
the acceleratrng voltage
is 300 volts and the distance between the condens—
.
ers
is
50 cm.
Usrng e/m = 1.76 X 107 e.m.u./g., nd the frequency of
the oscillator.
2—9. The cathode ray tube used in the measurement of e/m by the
“
helical ” method has X and Y deection plates at distances from the
screen
of 14 and 16 cm., respectively. Measurements are to be made
over
a
range of magnetic eld values which will produce one, two, and
three spirals with the X plates, and over a corresponding range with the
Y plates.
The accelerating potential will be held constant at 1000 volts.
What is the largest magnetic eld which will be required?
2—10. From the relation,
77752, calculate (a) the energy corresponding to the mass of one electron, (b) the energy corresponding to
one mass-unit and (c) the energy corresponding to one millimass-unit.
2—11. How many
electron volts are needed to accelerate (a) a proton,
(à) an (gg-particle, to the same velocity as that of an electron accelerated by
one electron volt?
2—12. An electron is accelerated by 17 volts and bent into a circular
path of radins r cm. by a magnetic eld of strength H oersteds. Show
that Hr = 3.37x/77.
2—13. One ampere
is passed through a single turn of wire of radins
13 cm.
Compute the eld intensity at a point
cm.
or the ax1s and
3 cm. out from the center of the coil.
Compare With tl1epntensrty
on the
'
'
t
t
nd at the center of the cor .
ax1s at the same clis ance ou a
0.056, 0.048 oersted)
2—14. Compute the mass of an electron and of the hydrogen
ion in
solution.
_
2—15. Calculate the force on the plate
of a two-electrode tube when
bombarded by electrons accelerated by 200 volts, the plate
being
6 milliamperes and g/m : 1,77 >< 107 e.m.u./gram,
assumrng
a)
of their momentum is given up
when they strike the plate.
(0.0
y£