Always use significant figure rules. remember that these rules apply to all numbers that are measurements. compute the resistance of a 90-cm length of copper wire with a 0.020 -cm2 cross-sectional area. ( = 1.8 x 10-6 ohm-cm) r = ohms a 4.0 x 10^-1 b 1.3 x 10^11 c 8.1 x 10^-3 d 2.5 x 10^9

Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=