Question
Wed February 06, 2013 By: Uma Sridharan

Two protons are moving with equal speed v in same direction.Ratio of electric force to magnetic force between is a) c/v2 b) v/c2 c)c/v d) v/c

Expert Reply
Thu February 07, 2013

Electric force, Fe= qE , where q = charge; E = electric field.

and, magnetic force, Fb= qvB, where q = charge; B = magnetic field.

Thus, FF b = q E/ q vB

=> FF E/Bv
We know: c = E/B
Thus,
FF = c * 1/v
=> FF c/v
Thus the required ratio is (c) c/v.
Ask the Expert