109 W 118 W 127 W 136 W

1. Suppose that a voltage surge produces 140 V for a moment in a 120 V-line. What will temporarily be the output of a 100 W lightbulb assuming its resistance does not change? • 109 W • 118 W • 127 W • 136 W

2. A solar panel measures 80 cm x 50 cm. In direct sunlight, the panel delivers 3.2 A at 15 V. If the intensity of sunlight is 1000 W/m2 , what is the efficiency of the solar panel in converting solar energy into electrical energy? • 24.0% • 18.0% • 12.0% • 6.0%

3. A steam turbine at an electric power plant delivers 4500 kW of power to an electrical generator which converts 95% of this mechanical energy into electrical energy. What is the current delivered by the generator if it delivers at 3600 V? • 0.66 x 103 A • 1.0 x 103 A • 1.19 x 103 A • 5.9 x 103 A

4. The heating coil of a hot water heater has a resistance of 20 ohm and operates at 210 V. How long a time is required to raise the temperature of 200 kg of water from 15°C to 80 °C? (the specific heat for water = 103 cal/kg-°C and 1.0 cal = 4.186 J) • 1.7 hr • 3.8 hr • 5.1 hr • 6.9 hr

5. The heating coil of a hot water heater has a resistance of 20 ohm and operates at 210 V. If electrical energy costs 5.5 cents per kW-hr, what does it cost to raise the 200 kg water temperature form 15°C to 80°C? (the specific heat of water = 103 cal/kg°C and 1.0 cal = 4.186 J) • 48 cents • 83 cents • 16 cents • 80 cents

6. An electric clothes dryer draws 15 A at 220 V. If the clothes put into the dryer have a mass of 7 kg when wet and 4 kg dry, how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water, Lvap = 2.26 x 106 J/kg.) • 55.1 min • 34.2 min • 20.0 min • 15.6 min

7. By what factor is the resistance of a copper wire changed when its temperature is increased from 20°C to 120°C? (the temperature coefficient of resistivity for copper = 3.9 x 10-3 /°C) • 0.72 • 1.06 • 1.39 • 1.44

8. If a lamp is measured to have a resistance of 120 ohms when it operates at a power of 100 W, what is the applied voltage? • 110 V • 120 V • 125 V • 220 V

9. If a lamp has a resistance of 120 ohms when it operates at a power of 100 W, what current does the lamp carry? • 2.10 A • 1.2 A • 0.91 A • 0.83 A

10. An electric toaster requires 1100 W at 110 Volts. What is the resistance of the heating coil? • 7.5 W • 9.0 W • 10.0 W • 11.0 W

11. If a 500 W heater carries a current of 4.0 A, how much does it cost to operate the heater for 30 min if electrical energy costs 6 cents per kW-hr? • 1.5 cents • 9.0 cents • 18.0 cents • 36.0 cents

12. A metal wire has a resistance of 10.00 ohms at a temperature of 20°C. If the same wire has a resistance of 10.55 ohms at 90°C, what is the resistance of this same wire when its temperature is -20°C? • 0.7 W • 9.69 W • 10.31 W • 13.8 W

13. If a 500 W heater carries a current of 4.0 A, what is the voltage across the ends of the heating element? • 2000 V • 125 V • 250 V • 0.008 V

14. If a 500 W heater carries a current of 4.0 A, what is the resistance of the heating element? • 85.7 W • 42.8 W • 31.3 W • 11.2 W

15. A metal wire has a resistance of 10.00 ohms at a temperature of 20°C. If the same wire has a resistance of 10.55 ohms at 90°, what is the temperature coefficient of resistivity of this metal? • 7.8 x 10-4/°C • 12.7 x 10-4/°C • 0.78 x 10-4/°C • 1.27 x 10-4/°C

16. A wire carries a steady current of 0.1 A over a period of 20 s. What total charge passes through the wire in this time interval? • 200 C • 20 C • 2.0 C • 0.005 C

17. A 0.20 m long metal wire has a radius of 1 cm and a resistance of 3.2 x 10-5 ohm. What is the resistivity of the metal? • 1.6 x 10-8 ohm-m • 5.0 x 10-8 ohm-m • 16.0 x 10-8 ohm-m • 160 x 10-8 ohm-m

18. A nichrome wire has a radius of 0.50 mm and a resistivity of 1.5 x 10-6 ohm-m. What is the resistance per unit length of this wire? • 0.0015 ohm-m • 0.95 ohm-m • 1.6 ohm-m • 1.9 ohm-m

19. A nichrome wire has a radius of 0.50 mm and a resistivity of 1.5 x 10-6 ohm-m. If the wire carries a current of 0.5 A, what is the potential difference per unit length along this wire? • 0.003 V/m • 0.95 V/m • 1.6 V/m • 1.9 V/m

20. When an electric current exists within a conducting wire, which of the following statements describes the condition of any accompanying electric field? • must be zero • must be parallel to current flow • must be anti-parallel to current flow • must be perpendicular to current flow

21. A high-voltage transmission line carries 1000 A at 700 kV for a distance of 100 miles. If the resistance in the wire is 1 W/mile, what is the power loss due to resistive losses? • 10 kW • 100 kW • 10 MW • 100 MW

22. A copper cable is to be designed to carry a current of 300 A with a power loss of only 2 Watts per meter. What is the required radius of the copper cable? (The resistivity of copper is 1.7 x 10-8 W-m) • 0.8 cm • 1.6 cm • 3.2 cm • 4.0 cm

23. An electric car is designed to run off a bank of 12-V batteries with total energy storage of 2 x 107 J. If the electric motor draws 8000 W, what is the current delivered to the motor? • 666 A • 444 A • 222 A • 111 A

24. A high-voltage transmission line carries 1000 A at 700,000 V. What is the maximum power carried in the line? • 700 MW • 370 MW • 100 MW • 70 MW

25. An electric car is designed to run off a bank of 12-V batteries with total energy storage of 2 x 107 J. If the electric motor draws 8000 W in moving the car at a steady speed of 20 m/s, how far will the car go before it is "out of juice"? • 25 km • 50 km • 100 km • 150 km

26. A color television set draws about 2.5 A when connected to 120 V. What is the cost (with electrical energy at 6¢/kWh) of running the color TV for 8 hours? • 1.4¢ • 3.0¢ • 14.4¢ • 30.0¢

27. A high voltage transmission line of diameter 2 cm and length 200 km carries a steady current of 1000 A. If the conductor is copper with a free charge density of 8 x 1028 electrons/m3 , how long does it take one electron to travel the full length of the cable? (q = 1.6 x 10-19 C) • 8 x 102 s • 8 x 104 s • 8 x 106 s • 8 x 108 s

28. The resistance of a platinum wire is to be calibrated for low-temperature work. A platinum wire with resistance 1 W at 20°C is immersed in liquid nitrogen at 77 K (-196°C). If the temperature response of the platinum wire in linear, what is the expected resistance of the platinum wire at -196°C?(aplatinum = 3.92 x 10-3 /°C) • 0.153 W • 0.232 W • 1.768 W • 1.847 W

29. Some superconductors are capable of carrying a very large quantity of current. If the measured current is 105 A, how many electrons are moving through the superconductor per second? (qe = 1.6 x 10-19 C) • 6.25 x 1023 • 3.12 x 1022 • 6.25 x 1021 • 3.12 x 1020

30. A platinum wire is utilized to determine the melting point of indium. The resistance of the platinum wire is 2 W at 20°C and increases to 3.072 W as the indium starts to melt. aplatinum = 3.92 x 10-3 /°C. What is the melting temperature of indium? • 137°C • 157°C • 351°C • 731°C

31. Which is not a force? • Gravity • Electrical force • Electromotive force • Friction

32. The unit of electric current, the ampere, is dimensionally equivalent to which of the following? • volt x ohm • volt/ohm • ohm x meter • volt/sec

33. The unit of electric resistance, the ohm, is dimensionally equivalent to which of the following? • volt/amp • volt x meter • amp/sec • amp/meter

34. What happens to the resistance of a superconductor when its temperature drops below the critical temperature? • equals that of a semiconductor of equal dimensions • increases by two • drops to zero • reduces to one-half

35. The quantity, electromotive force, is dimensionally equivalent to which of the following? • joule x meter • joule x coulomb • coulomb/ohm • joule/coulomb

36. The unit for rate of energy transformation, the watt, in an electric circuit is dimensionally equivalent to which of the following? • volt/sec • ampere x ohm • volt x ampere • volt/ohm

37. The current in an electron beam in a cathode-ray tube is measured to be 70 µ A. How many electrons hit the screen in 5 seconds? (qe = 1.6 x 10-19 C) • 2.19 x 1011 electrons • 8.75 x 1013 electrons • 2.19 x 1015 electrons • 8.75 x 1018 electrons

38. If a 6 V battery, with negligible internal resistance, and a 12 ohm resistor are connected in series, what is the amount of electrical energy transformed to heat per coul of charge that flows through the circuit? • 0.50 J • 3.0 J • 6.0 J • 72 J

39. If a 75 W lightbulb operates at a voltage of 120 V, what is the current in the bulb? • 0.63 A • 1.6 A • 9.0 x 103 A • 1.1 x 10-4 A

40. Tripling the current in a circuit with constant resistance has the effect of changing the power by what factor? • 0.33 • 1/9 • 3.0 • 9.0

41. Replacing a wire resistor with another of the same material and length but with three times the diameter will have the effect of changing the resistance by what factor? • 0.33 • 1/9 • 3.0 • 9.0

42. The size of the electric current in an electrical conductor is a function of which of the following? • velocity of charge carriers • conductor thickness • density of charge carriers • all of the choices are valid

43. A superconducting wire's chief characteristic is which of the following? • an extremely great length • a large cross-sectional area • an extremely high temperature • no resistance

44. When current is flowing in a superconductor, which statement is not true? • A battery keeps the current going. • Electrical charges are moving. • The resistance is zero. • No power is given off in the form of heat.

45. Ten coulombs of charge start from the negative terminal of a battery, flow through the battery and then leave the positive terminal through a wire, flow through a resistor and then return to the starting point on this closed circuit. In this complete process, the ten coulombs • do positive work on the battery. • receive heat energy from the resistor. • have a net loss of potential energy. • have no net change in potential energy.

46. Which process will double the power given off by a resistor? • Doubling the current while doubling the resistance • Doubling the current by making the resistance half as big • Doubling the current by doubling the voltage • Doubling the current while making the voltage half as big

47. In a carbon microphone, the change in resistance in the microphone as the sound wave moves the diaphragm back and forth is caused by the • change in length of the carbon resistance. • change in temperature of the carbon resistance. • change in voltage across the carbon resistance. • change in velocity of the carbon resistance.

48. Which is a unit of power? • Kilowatt-hour • Watt per sec • Ampere ohm • Joule per sec

49. If a certain resistor obeys Ohm's law, its resistance will change • as the voltage across the resistor changes. • as the current through the resistor changes. • as the energy given off by the electrons in their collisions changes. • none of the choices, since resistance is a constant for a given resistor.

50. Consider some material that has been cooled until it has become a superconductor. If it is cooled even further its resistance will • increase • decrease • stay constant and non-zero • none of the choices