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Problems 885 A S B C ε Figure Q28.29 Section 28.1 Electromotive Force A battery has an emf of 15.0 V. The terminal voltage of the battery is 11.6 V when it is delivering 20.0 W of 2. (a) What is the current in a 5.60-' resistor connected to a battery that has a 0.200-' internal resistance if the termi- 3. Two 1.50-V batteries — with their positive terminals in the same direction — are inserted in series into the barrel of a 4. An automobile battery has an emf of 12.6 V and an inter- 1. (b) when the starter motor is operated, taking an addi- Section 28.2 Resistors in Series and Parallel 5. The current in a loop circuit that has a resistance of R 1 is 2.00 A. The current is reduced to 1.60 A when an addi- 2 # 3.00 ' is added in series with R 1 . What is the value of R 1 ? 6. (a) Find the equivalent resistance between points a and b in Figure P28.6. (b) A potential difference of 34.0 V is 1, 2 , 3 = straightforward, intermediate, challenging = full solution available in the Student Solutions Manual and Study Guide = coached solution with hints available at http://www.pse.com = computer useful in solving problem = paired numerical and symbolic problems P R O B L E M S 9.00 Ω 4.00 Ω 10.0 Ω 7.00 Ω b a Figure P28.6 23. Suppose you fall from a building and on the way down grab a high-voltage wire. If the wire supports you as you 25. When electricians work with potentially live wires, they often use the backs of their hands or fingers to move wires. 26. What procedure would you use to try to save a person who is “frozen” to a live high-voltage wire without endangering 27. If it is the current through the body that determines how serious a shock will be, why do we see warnings of 28. Suppose you are flying a kite when it strikes a high-voltage wire. What factors determine how great a shock you 29. A series circuit consists of three identical lamps connected to a battery as shown in Figure Q28.29. When the switch S 24. 30. If your car’s headlights are on when you start the ignition, why do they dim while the car is starting? 31. A ski resort consists of a few chair lifts and several inter- connected downhill runs on the side of a mountain, with a |