4. A rod of length / has a uniform positive charge per unit length A and a total charge Q. Calculate the electric field at a point P that is located is located along the x-axis of the rod and a distance a from one end (see Fig. 3). dy = Adx F P5. Find the potential inside and outside a uniformly charged solid sphere whose radius is R and whose total charge is q. Use infinity as your reference point Compute the gradient of each V in the two regions (inside and outside), and check if it yields the correct field2. Four point charges are at the corners of a square side a. a. Determine the magnitude and direction of the electric field at the location of charge q. b. What is the resultant force on q? 2q q a 3q 4q a 3. Use Gauss's law to find the electric field inside a uniformly charged solid sphere of radius R (with charge density p). In this case, the imaginary Gaussian surface is inside the sphere with radius a. do = pdr