Find the magnetic field at point P for each of the steady current configurations shown in the figure. R (a) (b)

A battery is connected to wires that hand vertically (gravity acts down in the diagram).  Hooks at the ends of the wires hold a horizontal copper bar (the thick bar) of mass 0.6 kg and length 0.5 meters.  Another apparatus (not shown) can create a uniform magnetic field in the region of space given by the dashed rectangle.  The total resistance of the circuit is 1.20 Ohms and the battery supplies 24 Volts.  The magnetic field can be adjusted in strength until the bar lifts off of the hooks and levitates magnetically – not moving just above the hooks as shown. a) Determine the necessary direction of the magnetic field in the dashed rectangle. b) Calculate the required magnitude of the magnetic field.

A flip coil is a relatively simple device used to measure a magnetic field. It consists of a circular coil of N turns wound with fine conducting wire. The coil is attached to a ballistic galvanometer, a device that measures the total charge that passes through it. The coil is placed in a magnetic field B → such that its face is perpendicular to the field. It is then flipped through 180°, and the total charge Q that flows through the galvanometer is measured. (a) If the total resistance of the coil and galvanometer is R, what is the relationship between B and Q? Because the coil is very small, you can assume that B → is uniform over it. (b) How can you determine whether or not the magnetic field is perpendicular to the face of the coil?

Find the direction and magnitude of the minimum velocity of charge q = +2e that will produce the magnetic force F shown in the figure below. (Measure the angle counterclockwise from the x axis in the xz plane. Take the magnitudes of F as 1.96 x 10-11 N and the magnitude of B as 2.19 T.) magnitude   direction