Back in the day, a standard television tube would work by accelerating electrons
ID: 1322974 • Letter: B
Question
Back in the day, a standard television tube would work by accelerating electronsthrough an electrostatic potential and then bending them with a magnetic field as shown in thefigure at the right. If the electrostaticpotential difference used to acceleratethe electrons through the anodes is11,000 Volts, estimate the maximumstrength of a magnetic field needed tocontrol the deflection of an electronbeam. You will have to estimatereasonable parameters for the requireddistances.
Back in the day, a standard television tube would work by accelerating electronsthrough an electrostatic potential and then bending them with a magnetic field as shown in thefigure at the right. If the electrostaticpotential difference used to acceleratethe electrons through the anodes is11,000 Volts, estimate the maximumstrength of a magnetic field needed tocontrol the deflection of an electronbeam. You will have to estimatereasonable parameters for the requireddistances.Explanation / Answer
the condition for the controlling of the deflection of electron beam
elecric force on Electron = magnetic force on the electron
q*E = q*v*B...
here v is the speed of the electron
E = v*B...
but work done on the electon to acclearte it = q*V = chenage in Kinetic energy of the electron
q*V = 0.5*m*v^2..
speed v= sqrt(q*V/(0.5*m)) = sqrt(1.6*10^-19*11000/(0.5*9.1*10^-31))
v = 6.219*10^7 m/s...
E is not given in the problem
if E is known
then Maximum magnetic field is B = E/v =E / (6.219*10^7)
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