The magnetic field `bar(dB)` due to a small current element `bar(dl)` at a distance `vec(r)` and carrying current `'I'` is

Options

A. `vec(dB) = (mu_0)/(4pi)i( (vec(dl) xx vec r)/(r ) ) `
B. `vec(dB) = (mu_0)/(4pi) i^2 ( (vecdl xx vecr)/(r^2) )`
C. `vecdB = (mu_0 )/(4pi) i^3 ( (vecdl xx vecr)/(r ) ) `
D. `vecdB = (mu_0)/(4pi) i( (vecdl xx vecr)/(r^3) )`

Answer

D