Question

Suppose that a third wire, carrying another current i0 out of the page, passes through point P. Draw a vector on the diagram to indicate the magnetic force, if any, exerted on the current in the new wire at P. If the magnitude of the force is zero, indicate that explicitly. Explain your reasoning.

Answer 1

The two existing wires carry currents
`I_1` and
`I_2` into the page are currents generate magnetic fields around them, which can be determined using the right-hand rule.

If we apply the right-hand rule for each wire, we can determine that the magnetic field at point P due to both wires will be directed out of the page. The new wire carries a current
`I_0` out of the page and this current interacts with the magnetic field at point P, which can exert a force on the wire.

The direction of the force on the new wire can be determined using the right-hand rule again. In this case, considering the out-of-page magnetic field and the out-of-page current in the new wire, the right-hand rule indicates the force will be directed to the right.