Suppose you have an infinitely long cylindrical current carrying wire with radius a=13cm  . The current density of the wire is J=cr 2/ a 2    where c=3A/m 2   is a constant. a)  Find the enclosed current at radial distance r=(0.6a)cm  b)  Find the magnitude of magnetic field at radial distance r=(0.6a)cm  . c)  Find the magnitude of magnetic field at radial distance d=73cm  .

One solenoid is inside the other solenoid. Both solenoids have length L and N turns. The radius of the inner solenoid is 2R and the radius of the outer solenoid is 3R. The inner solenoid carries current 41 and the outer solenoid carries current l in opposite directions as shown. What is the magnetic field at a distance R from the central axis? Both solenoids are long and thin, i.e., L >> R. > +x

A rod with mass m = 0.720 kg and radius r = 6.00 cm rests on two parallel rails, as shown in the figure. The rails are separated by a distance d = 12.0 cm and have length L = 45. cm.The rod carries a current I = 48.0 A in the direction shown in the figure and rolls on the rails without slipping. There is a uniform magnetic field of magnitude B = 0.240 T perpendicular to the rails and the rod. If the rod starts from rest, what is its speed when it leaves the rails?