(II) The betatron, a device used to accelerate electrons to high energy, consists of a circular vacuum tube placed in a magnetic field (Fig. 29–48), into which electrons are injected. The electromagnet produces a field that (1) keeps the electrons in their circular orbit inside the tube, and (2) increases the speed of the electrons when B changes. ( a ) Explain how the electrons are accelerated. (See Fig. 29–48.) ( b ) In what directions are the electrons moving in Fig. 29–48 (give directions as if looking down from above)? ( c ) Should B increase or decrease to accelerate the electrons? ( d ) The magnetic field is actually 60 Hz ac; show that the electrons can be accelerated only during 1 4 of a cycle ( 1 240 s ) . (During this time they make hundreds of thousands of revolutions and acquire very high energy.)
(II) The betatron, a device used to accelerate electrons to high energy, consists of a circular vacuum tube placed in a magnetic field (Fig. 29–48), into which electrons are injected. The electromagnet produces a field that (1) keeps the electrons in their circular orbit inside the tube, and (2) increases the speed of the electrons when B changes. ( a ) Explain how the electrons are accelerated. (See Fig. 29–48.) ( b ) In what directions are the electrons moving in Fig. 29–48 (give directions as if looking down from above)? ( c ) Should B increase or decrease to accelerate the electrons? ( d ) The magnetic field is actually 60 Hz ac; show that the electrons can be accelerated only during 1 4 of a cycle ( 1 240 s ) . (During this time they make hundreds of thousands of revolutions and acquire very high energy.)
(II) The betatron, a device used to accelerate electrons to high energy, consists of a circular vacuum tube placed in a magnetic field (Fig. 29–48), into which electrons are injected. The electromagnet produces a field that (1) keeps the electrons in their circular orbit inside the tube, and (2) increases the speed of the electrons when B changes. (a) Explain how the electrons are accelerated. (See Fig. 29–48.) (b) In what directions are the electrons moving in Fig. 29–48 (give directions as if looking down from above)? (c) Should B increase or decrease to accelerate the electrons? (d) The magnetic field is actually 60 Hz ac; show that the electrons can be accelerated only during
1
4
of a cycle
(
1
240
s
)
. (During this time they make hundreds of thousands of revolutions and acquire very high energy.)
Interaction between an electric field and a magnetic field.
(II) Suppose the electric field between the electric plates inthe mass spectrometer of Fig. 20–41 is 2.88 x 104 V/m andthe magnetic fields B=B'=0.68 T are The source contains carbon isotopes of mass numbers 12, 13, and 14 from a long-dead piece of a tree. (To estimate masses of the atoms, multiply by 1.6 x 10-27 kg) How far apart are the linesformed by the singly charged ions of each type on the photographic film? What if the ions were doubly charged?
(III) A 3.40-g bullet moves with a speed of 155 m/s per-
pendicular to the Earth's magnetic field of 5.00 × 10-5 T.
If the bullet possesses a net charge of 18.5 × 10-° C, by
what distance will it be deflected from its path due to the
Earth's magnetic field after it has traveled 1.50 km?
Two ions have the same mass, but one is singly ionized andthe other is doubly ionized. How will their positions on thefilm of a mass spectrometer (Fig. 20–41) differ? Explain.
Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
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