Homework 6

Physical Science Textbook - Pages 138 - 139

Chap. 5- Parallel problem groupB: 5, 6, 7, 11, 13, 14, 17, 18

5. What is the magnitude of the least possible current that could theoretically exist? 6. There is a current of 0.83 A through a lightbulb in a 120 V circuit. What is the resistance of this lightbulb? 7. What is the voltage across a 60.0 2 resistor with a current of 3 1/3 amp? 8. A 10.0 2 lightbulb is connected to a 12.0 V battery. (a) What current flows through the bulb? (b) What is the power of the bulb? 9. A lightbulb designed to operate in a 120.0 V circuit has a resistance of 192 2. At what rate does the bulb use electric energy? 10. What is the monthly energy cost of leaving a 60 W bulb on continuously if electricity costs $0.10 per k Wh? 11. An electric motor draws a current of 11.5 A in a 240 V circuit. What is the power of this motor in W? 12. A swimming pool requiring a 2.0 hp motor to filter and circulate the water runs for 18 hours a day. What is the monthly electrical cost for running this pool pump if electricity costs $0.10 per k Wh? 13. Is it possible for two people to simultaneously operate 1,300 W hair dryers on the same 120 V circuit without tripping a 15 A circuit breaker? Explain. 14. A step-up transformer has a primary coil with 100 loops and a secondary coil with 1,500 loops. If the primary coil is supplied with a household current of 120 V and 15 A, (a) what voltage is produced in the secondary circuit? (b) what current flows in the secondary circuit? 15. The step-down transformer in a local neighborhood reduces the voltage from a 7,200 V line to 120 V. (a) If there are 125 loops on the secondary, how many are on the primary coil? (b) What current does the transformer draw from the line if the current in the secondary is 36 A? (c) What are the power input and output? 16. A step-down transformer connected to a 120 V electric generator has 30 loops on the primary for each loop in the secondary. (a) What is the voltage of the secondary? (b) If the transformer has a 90.0 A current in the primary, what is the current in the secondary? (c) What are the power input and output? 17. What is the power of an 8.0-ohm bulb when three such bulbs are connected in a 12-volt series circuit