P132a Problem Set 5

Due at the beginning of class on FRIDAY, 11 February 2000.

Chapter 33: Problems 48, 51

Chapter 34: Problems 12, 22, 41, 42, 48

8. The electrons in the beam of a television tube have an energy of 12 keV. Assume that the earth's magnetic field in Chicago is vertical (not a bad assumption) and points downward, with a magnitude B = 5.5 x 10^-5 Tesla (or 0.55 gauss). The tube of the TV is oriented so that the electrons move horizontally from south to north (see sketch).

• (a) What is the speed of an electron with an energy of 12 keV?
• (b) In what direction will the electrons in the beam deflect due to the earth's magnetic field?
• (c) What is the acceleration of a given electron as a result of the magnetic force on it?
• (d) How far will the beam deflect in moving 20 cm through the television tube?