A long vertical wire carries an unknown current. Coaxial with the wire is a long, thin, cylindrical conducting surface that carries a current of 30 mA upward. The cylindrical surface has a radius of 3.0 mm. If the magnitude of the magnetic field at a point 5.0 mm from the wire is 1.0 mT, what are the (a) size and (b) direction of the current in the wire?

Two long parallel wires are a distance d apart. The current in one wire is 10 A and the current in the other wire is 30 A. The currents are in the same direction. If the 30-A current is increased to 50 A, by what factor does the magnitude of the magnetic field midway between the wires change?

there are three parallel wires in a row. The outside two have currents directed in the + X direction and the middle is in the -X direction. What direction is the magnetic field on one of the outside wires?

A wire carrying a current is shaped in the form of a circular arc of angle 60° and radius 5.0 mm. If the magnetic field strength that this current produces at point A in the center of the arc is 22.0 µT, what is the magnitude of the current that flows through the arc? Give your answer in Amp. If the B field at A is out of the page, what is the direction of the current on the arc of wire? (select one of the following: cw, ccw, right, left, into or out) A 9 ME