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Asked in GUJCET 2009 · Circular motion: radius, period and energy
Given: an electron and a proton with the same linear momentum p, each entering perpendicular to the same field B.
Idea: the magnetic force supplies the centripetal force, qvB=(mv²)/r, so r=(mv)/(qB)=p/(qB).
Written this way the radius depends only on the momentum, the charge and the field — not on the mass separately.
The electron and the proton carry charge of the same magnitude e, and p and B are the same for both.
So rₑ=p/(eB)=rₚ and the ratio is 1.
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