Early black-and-white television sets used an electron beam to draw a picture on

Question

Early black-and-white television sets used an electron beam to draw a picture on the screen. The electrons in the beam were accelerated by a voltage of 3.0 kV ; the beam was then steered to different points on the screen by coils of wire that produced a magnetic field of up to 0.65 T. Part A: What is the speed of electrons in the beam? Correct Answer: v= 3.2 x 10^7 m/s Part B: What acceleration do they experience due to the magnetic field, assuming that it is perpendicular to their path? Correct Answer: 3.66 x 10 ^18 m/s2 Part C: If the electrons were to complete a full circular orbit, what would be the radius? Part C is what I cannot solve and need help with. Please and thank you! = )

Explanation / Answer

K.E. = P.E.
1/2 m v^2 = e*Voltage
v = sqrt(2*e*Voltage/m)

b) F = q v B
m a = q v B
a = q v B / m

c) a = v^2 / r ==> r = v^2/a

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