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Question: Answered & Verified by Expert
A proton beam enters a magnetic field of \( 10^{-4} \mathrm{~Wb} m^{-2} \) normally. If the specific charge of the
proton is \( 10^{11} \mathrm{C} \mathrm{kg}^{-1} \) and its velocity is \( 10^{9} \mathrm{~ms}^{-1} \), then the radius of the circle described will
be
PhysicsElectrostaticsKCETKCET 2015
Options:
  • A \( 0.1 \mathrm{~m} \)
  • B \( 10 \mathrm{~m} \)
  • C \( 100 \mathrm{~m} \)
  • D \( 1 \mathrm{~m} \)
Solution:
2977 Upvotes Verified Answer
The correct answer is: \( 100 \mathrm{~m} \)
Magnetic field \( B=10^{-4} \mathrm{~W} \mathrm{bm}^{-2} \), charge \( q=10^{11} \mathrm{Ck} g^{-1} \)
velocity \( v=10^{9} \mathrm{~ms}^{-1} \)
Now, radius of the circle described by proton is
\( r=\frac{m v}{q B}=\frac{v}{\left(\frac{q}{m}\right) \times B}=\frac{10^{9}}{10^{11} \times 10^{-4}}=10^{2} \)
Therefore, radius of circle is \( 100 \mathrm{~m} \).

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