Chapter 20: Electric Circuits Example Problems R L A RSeries Rn I 1 RParallel V R VR2 PR IR VR IR2 R 1 Rn Vn Rn Rseries VS R V n 0 Example 20.1 a. A 1.0-mm-diameter, 20-cm-long copper wire carries a 3.0 A current. What is the potential difference between the ends of the wire? Hint: ρCu = 1.7 × 10−8 Ω∙m b. A motorcyclist is making an electric vest that, when connected to the motorcycle's 12 V battery, will warm her on cold rides. She is using 0.25-mm-diameter copper wire, and she wants a current of 4.0 A in the wire. What length wire must she use? Example 20.2 The power rating of a light bulb is the power it dissipates when connected across a 120V potential difference. What is the resistance of (a) a 100-W and 60-W bulb? (b) How much current does each bulb draw in normal use? (c) Car headlights are either a low or high beam, is there more or less resistance in the high-beam filament? Example 20.3 Determine the equivalent resistance of (a) circuit-1 and (b) circuit-2. Example 20.4 For each circuit, compute the (a) equivalent resistance and (b) current through each resistor. Circuit 1 Circuit 2 Example 20.5 For a circuit shown, find the current through and the voltage across each resistor.