The picture tube In a television uses magnetic deflection coils rather than elec

Question

The picture tube In a television uses magnetic deflection coils rather than electric deflection plates. Suppose an electron beam is accelerated through a 55.0 kV potential difference and then through a region of uniform magnetic field 1.00 cm wide. The screen is located 8.0 cm from the center of the cots and is 50.0 cm wide. When the field is turned off, the electron beam hits the center of the screen. What field magnitude is necessary to deflect the beam to the side of the screen? Iqnore relative corrections. mT

Explanation / Answer

theta = tan^-1(25/8) = 72.255 degree

The electron beam, at the point where it enters the magnetic field region, travels to the right, but the beam, at the

point it where emerges from the magnetic field region, has been deflected from its original direction by angle theta .

R = 1cm/sin72.255 = 1.05 cm

energy conservation

mv^/2 = qV

v = sqrt(2qV/m)

v = 1.39 x 10^8 m/s

mv^2/R = qvB

B = mv/qR

B = 0.075 T

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