Problem

Equal currents are flowing in three infinitely long wires along positive

x

y

and

z

-directions. The magnetic field at a point

(0, 0, -a)

would be (

i

= current in each wire) (a)

\frac{\mu_0 i}{2\pi a} (\hat{j} - \hat{i})

(b)

\frac{\mu_0 i}{2\pi a} (\hat{i} - \hat{j})

(c)

\frac{\mu_0 i}{2\pi a} (\hat{i} + \hat{j})

(d)

\frac{\mu_0 i}{2\pi a} (-\hat{i} - \hat{j})