There are six identical, circular, metal rings centered on the faces of a cube. Their diameters are equal the side lengths ’a’ of the cube. They all have equal currents ’I’ running through them. How must the currents run (maybe a picture would help) in order to generate the biggest B field at the center of the cube, and how large is that field?

An electron experiences a force of 2.5x10-10 N [down] exerted on it upon entering a magnetic field directed into the page with magnitude 3.1 T. If the electron was accelerated from rest by an electric field before entering the magnetic field, what was the potential difference between the plates? What is the direction of the electric field between the plates?

2) a) Which physical law is the basis for the continuity equation? b) Write continuity equation in differential form. c) Write two equations that each stand for magnetostatic case. d) An agglomeration of protons, that we shall treat as a point, explodes. 10 protons per second fly in all directions on average. What is the sign of div ?⃗(?⃗) at the position of the agglomerate? e) Write out div ?⃗(����⃗). Hint: remember what a delta function does to a volume integral.