A charged particle moves with velocity `vec v = a hat i + d hat j` in a magnetic field `vec B = A hat i + D hat j.` The force acting on the particle has magnitude F. Then,

Options

A. F = 0, if aD = dA
B. F = 0, if aD = – dA
C. F = 0, if aA = – dD
D. `F prop (a^(2)+d^(2))^(1//2)xx(A^(2)+D^(2))^(1//2)`

Answer

A

Explanation

`vecv=ai+dhatj, vecB=Ahati+Dhatj`
`vecF=q(vecvxxvecB),vecF=q(aD-Ad)hatkimpliesvecF=0`, if `aD=Ad`