Solve these physics exams questions with detailed solutions. I took these questions from past exams. I want to revise on these it's like to come up in my upcoming exams. Be able to draw diagrams. INCLUDE DIAGRAMS. Handwritten notes will do.

Be able to derive the formulae for electric field in a pn junction by integrating the charge density (given Gauss's equation) on both sides of the junction. Understand the effect of bias (positive and negative) on a pn junction in terms of its effect on the bandstructure and therefore current. Be able to explain how a JFET works on terms of voltage control of its depletion regions formed at the pn junctions. Be able to draw diagrams of a JFET under different bias conditions. Be able to draw IV versus gate voltage for a JFET. Be able to explain and draw circuit diagrams of how a JFET can act as a small signal amplifier