Review Calculate E, V, and F Units: E (c/m 2 ), V (c/m=V), and F (c 2 /m 2 =N). Superposition Principle 1. Point charges Equation of motion F=ma, S=v 0 t+1/2at 2 Energy Conservation qV=  K (Kinetic energy change)

2. Continuous Charge Distribution g. Check the units. Problem solving strategies: a. Setup a coordinate; Label positions of charge location, point of interests, etc. b. Choose a small element (line segment in 1D, small area in 2D, and small volume in 3D). Avoid choosing special points such as center, end points, midpoint, etc. c. Consider the chosen small element as a point charge and use the formula for point charge to write down dE, dV, or dF, which all depends on charges (dq) carried by the small element. d. Express dq in terms of total charges or density times the small length ( dl), area (  dA) or volume (  dV). e. The total E, V, or F is the sum of all these small element. (integral). f. Properly determine the limits and evaluate the integration.

3. Continuous Charge distribution with symmetries Use Gauss' law. Common geometries are sphere, cylinder, and sheet. Problem solving strategies: a. Choose a point of interest (where you want to calculate E) b. Choose an appropriate Gaussian Surface that contains that point on the surface. 1) E || dA, or E  dA, or combination of two. 2) E has to have the same magnitude on the Gaussian surface. c. Evaluate the integration. Typically you can take E out of integration if you properly choose a Gaussian surface. Consequently, you just need to evaluate the area of the Gaussian surface. Symmetry of EGaussian Surface Spherical (point & spherical charges)Sphere Cylindrical (line charge)Cylinder Planar (sheet of charge)Box or cylinder

4. Calculating Potential Notice that states i and f could be any two points. For examples, i and f could two plates of a capacitor, one sphere to another sphere, etc. Last hint: Don't forget energy conservation principle.