As measured by observers in a reference frame S, a particle havingcharge q moves
with velocity v in a magnetic field B and an electric field E . Theresulting force on
the particle is then measured to be F = q(E + v Ã B) . Anotherobserver moves along
with the charged particle and measures its charge to be q also butmeasures the
electric field to be E ' . If both observers are to measure thesame force, F , show that
E'=E+vÃB.

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