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4. Moving charges and magnetism — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics4. Moving charges and magnetism1 Mark
MCQ
Assertion : Cyclotron does not accelerate electron.

Reason : Mass of the electrons is very small

  • A
    If the Assertion is correct but Reason is incorrect.
  • B
    If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
  • ✓
    If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
  • D
    If both the Assertion and Reason are incorrect.
✓

Answer

Correct option: C.
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
c
Cyclotron does not accelerate electron because mass of electron is very small. It gets accelerated very appreciably as a result of which its mass increases. It result is mismatch between frequency of $a.c.$ used and frequency of rotation of electron in the Dee’s. So cyclotron stops accelerating electrons after some time.

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