Current density: A proton beam that carries a total current…

Current density: A proton beam that carries a total current of 1.3 mA has 10.0 mm diameter. The current density in the proton beam increases linearly with distance from the center. This is expressed mathematically as J(r) = J0 (r/R), where R is the radius of the beam and J0 is the current density at the edge. Determine the value of J0.

Parallel-plate capacitors: Each plate of a parallel-plate ai…

Parallel-plate capacitors: Each plate of a parallel-plate air-filled capacitor has an area of  0.0020 m2, and the separation of the plates is 0.020 mm An electric field of 3.9 x 106 V/m is present between the plates. What is the surface charge density on the plates? (

Ohm’s law: A cylindrical wire of radius  2.0 mm carries a cu…

Ohm’s law: A cylindrical wire of radius  2.0 mm carries a current of  2.5 A. The potential difference between points on the wire that are  46 m apart is  3.7 V.(a) What is the electric field in the wire?  (2 points)(b) What is the resistivity of the material of which the wire is made? (2 points)