Easy MCQ +4 / -1 PYQ · JEE Mains 2020

A beam of protons with speed 4 × 105 ms–1 enters a uniform magnetic field of 0.3 T at an angle of 60° to the magnetic field. The pitch of the resulting helical path of protons is close to :
(Mass of the proton = 1.67 $\times$ 10–27 kg, charge
of the proton = 1.69 $\times$ 10–19 C)

  1. A 2 cm
  2. B 12 cm
  3. C 5 cm
  4. D 4 cm Correct answer

Solution

Pitch = $\frac{2\pi m}{qB}$ vcos$\theta$ <br><br>= $${{2\left( {3.14} \right)\left( {1.67 \times {{10}^{ - 27}}} \right) \times 4 \times {{10}^5} \times \cos 60} \over {\left( {1.69 \times {{10}^{ - 19}}} \right)\left( {0.3} \right)}}$$ <br><br>= 0.04 m = 4 cm

About this question

Subject: Physics · Chapter: Magnetic Effects of Current · Topic: Biot-Savart Law

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