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Lesson 8.01 Current Resistance and Power Self-Check Quiz 1. A constant 10 A current flows in a circuit with a resistance of 200 ohm. The net charge passing through any point in the circuit during a 1 minute interval is _______. a. 200C b. 400C c. 600C d. 1200C Answer: _____ 2. If a 75-W light bulb operates at a voltage of 120 V, what is the current in the bulb? a. 0.63 A b. 0.78 A c. 0.85 A d. 1.1 A Answer: _____ 3. The heating coil of a water heater has a resistance of 20 ohm and operates at 210 V. How long does it take to raise the temperature of 200 kg of water from 15oC to 80oC? (cwater = 4186 J/kg*oC) a. 1.7 hr b. 3.8 hr c. 5.1 hr d. 6.9 hr Answer: _____ 4. Electrical resistance in a wire depends on the wire's _____________. a. conductivity b. length c. thickness d. All of the above e. None of the above Answer: _____ 5. Toaster uses a nichrome heating coil and operates at 120 V. When the toaster is turned on at 20oC, the current in the cold coil is 1.5 A. When the coil warms up, the current has a value of 1.3 A. If the thermal coefficient of resistivity for nichrome is 4.5*10-4 1/Co, what is the temperature of the coil? a. 486o b. 362o c. 256o d. 163o e. 68.2o Answer: _____ 6. A 1500 resistor is rated at 2.75 W. What is the maximum potential difference on the resistor? a. 8 V b. 14 V c. 25 V d. 38 V e. 64 V Answer: _____ 7. A 0.20 meter long metal wire has a radius of 1 cm and a resistance of 3.2*10-5. What is the resistivity of the metal? a. 1.6*10-8 b. 5.0*10 -8 c. 16.0*10 d. 160*10 -8 -8 m m m m Answer: _____ 8. A 500-W heater carries a current of 4.0 A. What is the resistance of the heating element? a. 85.7 b. 42.8 c. 31.3 d. 11.2 Answer: _____ 9. A 5.5 meter long Aluminum wire has resistance of 0.40 2.82x10-8 m, = = 4.29x10-3C-1. Its conductivity is a. 2.5x103 b. 3.55x107 ( , -1 m) -1 /m c. 233. Answer: _____ 10. Electrical resistance in a wire depends on the wire's __________. a. length b. diameter c. resisistivity d. All of the above e. None of the above Answer: _____ 11. A copper cable carries a current of 300. If the power loss is 2 W per meter, find the radius of the cable. (The resistivity of copper is 1.7*10-4 m.) a. 0.8 cm b. 1.6 cm c. 3.2 cm d. 4.0 cm Answer: _____