Magnetic Field of a Wire

A straight wire carries a current of 30 A in the north direction. Find the magnetic field 3.0 m directly below the wire.

How do magnets work?

Two long straight parallel wires are separated by a distance of 25 cm. One is carrying a current of 2 A, the other 4 A (the currents are aimed in the same direction) . What is the magnetic field, $\vec{B}$ at a point directly in the middle of the wires?

The picture below depicts a wire carrying a current I = 25.0 A. The shape of the wire is two combined arcs with r$_1$ = 9.0 cm and r$_2$ = 6.0 cm. Find the magnetic field at the center of the arcs (in blue).