The physical terms might not be the right english ones, I am not english. I hope you will understand anyway. I need help with the 3 following exercises, if anyone could dedicate some time to them I would be really grateful. Thank you. 1) Determine the electric and potential fields in all the space for a system composed of a sphere of radius=R, equally charged with charge=Q, surrounded by a spherical conductor crown with internal radius=R and external radius=r. 2) A proton is fired toward another proton, which is steady at a great distance, with speed v= 2.4 * 10^8 m/s. Find the minimal distance between the two protons. 3) We have a vertical electric field. How intense must it be and what direction must it have to hold a particle in equilibrium? The particle has mass = 10^-8 g and is charged with q= 1.7 * 10^-9 C. Thank you very much in advance.