Magnetism: Force on Charge in Combined Fields MCQ

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Force on Charge in Combined FieldsMediumQuestion 20201

Question

A proton moves with velocity 3×10⁶ m/s in a magnetic field of 0.2 T perpendicular to its velocity. The radius of its circular path is (m_p = 1.67×10⁻²⁷ kg, q = 1.6×10⁻¹⁹ C):

A
0.157 m
Correct
B
0.314 m
C
0.078 m
D
0.628 m

Correct answer

0.157 m

Explanation

r = mv/(qB) = (1.67×10⁻²⁷ × 3×10⁶)/(1.6×10⁻¹⁹ × 0.2) = 5.01×10⁻²¹/3.2×10⁻²⁰ ≈ 0.157 m.

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