Phy 132 - Assignment 5 A. Whether terms for resistors are positive or negative comes from remembering that current flows from higher to lower voltage. (+ to -.) B. 1. 2. C. D. 1. 25 W has the higher resistance. Power = V2/R, so with the same voltage on both, more ohms means less watts. 100 W carries more current, by V = IR. (In words instead of equations, more current (more electrons per second) is needed through the 100 W bulb to deliver the greater power (greater energy per second). The 100 W bulb must have less resistance to let that greater current through.) 2. E. 1. For a current to flow, it needs someplace to flow to. The bird, touching nothing but the wire, is not part of a complete circuit. The child is in contact with the ground; if the kite’s string was damp enough to be conducting – zap. 2. Every term in the summation should be a voltage. The I2 term has amps for its unit, not volts. 3. F. 1. When no current is flowing through the battery. (The potential difference between a battery’s terminals is E – Ir, where r is the internal resistance.) 2. Knock the person’s hand from the wire using some insulating object. (A meterstick if it isn't metal, or a shoe if it isn't damp, or …) Do not touch the person directly unless you are absolutely sure that you are not grounded. 3.