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Electron, Photon, Photo-electric Effect and X-Rays — JEE physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceJEE physicsElectron, Photon, Photo-electric Effect and X-Rays1 Mark
MCQ
A cathode emits $1.8 \times 10^{14}$ electrons per second, when heated. When $400 \mathrm{~V}$ is applied to anode all the emitted electrons reach the anode. The charge on electron is $1.6 \times 10^{-19} \mathrm{C}$. The maximum anode current is
  • A
    $2.7 \mu \mathrm{A}$
  • ✓
    $29 \mu A$
  • C
    $72 \mu \mathrm{A}$
  • D
    $29 m A$
✓

Answer

Correct option: B.
$29 \mu A$
$ i=\frac{Q}{t}=\frac{n e}{t}=1.8 \times 10^{14} \times 1.6 \times 10^{-19}=28.8 \times 10^{-6} \mathrm{~A}$
$ =29 \mu \mathrm{A}$

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