Do magnetic forces obey Newton's third law. Verify for two current elements dl1= dl i located at the origin and dl2 = dl j located at(0, R, 0). Both carry current I.

This is a Short Answer Type Questions as classified in NCERT Exemplar Explanation- In Biot-Savart's law, magnetic field B is parallel (II) to id * r and idl have its direction along the direction of flow of current. Here, for the direction of magnetic field, At dl2, located at (0, R,0) due to wire d1 is given by B I | dl * r or I *j (because point (0, R,0)lies on y-axis), but I * j= k So, the direction of magnetic field at d2 is along z-direction. The direction of magnetic force exerted at d2 because of the first wire along the x-axis F =i (l * B) i.e., F| (i *k ) or along− j direction. Therefore, force due to dl1 on dl2 is non-zero. Now, for the direction of magnetic field, At d1, located at (0,0,0) due to wire d2 is given by B I | dl * r or j *−j (because origin lies on y-direction w.r.t. point (0, R,0).), but j *−j =0. So, the magnetic field at d1 does not exist. Force due to dl2 on dl1 is zero. So, magnetic forces do not obey Newton's third law.