A charged particle moves with velocity $\overrightarrow{\mathrm{v}}=\left(\mathrm{a}\widehat{\mathrm{i}}+\mathrm{d}\widehat{\mathrm{j}}\right)$ in a magnetic field $\overrightarrow{\mathrm{B}}=\left(\mathrm{A}\widehat{\mathrm{i}}+\mathrm{D}\widehat{\mathrm{j}}\right)$ the force acting on the particle has magnitude F

• A

  F = 0 if aD = Ad

• B

  F = 0  if aD = –Ad

• C

  F = 0  if aA = –dD 

• D

  $\mathrm{F}\propto {\left({\mathrm{a}}^2+{\mathrm{d}}^2\right)}^{\frac{1}{2}}\times {\left({\mathrm{A}}^2+{\mathrm{D}}^2\right)}^{\frac{1}{2}}$