Concept explainers
The electron beam inside a television picture tube is 0.40 mm in diameter and carries a current of 50 μA. This electron beam impinges on the inside of the picture tube screen.
a. How many electrons strike the screen each second?
b. The electrons move with a velocity of 4.0 × 107 m/s. What electric field strength is needed to accelerate electrons from rest to this velocity in a distance of 5.0 mm?
c. Each electron transfers its kinetic energy to the picture tube screen upon impact. What is the power delivered to the screen by the electron beam?
Hint: What potential difference produced the field that accelerated electrons? This is an emf.
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