4 ) Which of the following statements is/are true? (briefly explain your reasoning for each) a) The E-field is zero midway between two "-" charges of equal magnitude. b) The E-field is zero midway between a "+" and a "-" charge of equal magnitude. c) The electric potential is zero midway between a "+" and a "-" charge of equal magnitude. Describe in your own words what "potential energy" means in physics, and then tell us what you think "electric potential energy" means. C What is the principle of superposition? (Describe briefly and in your own words what this principle means for electric fields, and what it means for electric potentials. (Is there anything fundamentally different about the two?)