The current in an electron beam in a cathode-ray tube is measured to be 50 µA.How many electrons hit the screen in 4.0 s? (e = 1.6 × 10−¹⁹ C) A) 2.5 × 10¹¹ electrons B) 2 × 10¹³ electrons C) 1.2 × 10¹⁵ electrons D) 3.1× 10¹⁸ electrons E) 1.6 × 10¹⁷ electrons

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Quizplus · Accepted Answer

The number of electrons is calculated by dividing the total charge by the charge of one electron. Total charge = current × time = 50 µA × 4 s = 200 µC = 200 × 10^-6 C. Number of electrons = (200 × 10^-6 C) / (1.6 × 10^-19 C/electron) = 1.25 × 10^15 electrons, which rounds to 1.2 × 10^15 electrons.

The Current in an Electron Beam in a Cathode-Ray Tube