Transcription of Sample Exam #3 Electricity Physics 103 Spring 2011 1. Ω ...
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Sample Exam #3 Electricity Physics 103 Spring 2011 1. Ω ...
Sample Exam #3 Electricity Physics 103 Spring 2011. 1. An electric heater is constructed by applying a potential difference of 110 V across a wire with a resistance of . What is the power rating of the heater? a. kW. b. kW. c. kW. d. kW. e. 60 kW. I = 110V = 22 A.. P = I2R = (22)2 (5 ) = 2420 W = kW. 2. A resistor has a current of A in it for min. How many electrons pass through the resistor during this time interval? a. 1021. b. 1021. c. 1021. d. 1021. e. 1021. Q. I= ;. t Q = I t = 3 5 60 = 900C. Q = q N. N = I t / q = 900C 10 19 C = 1021. 3. A wire (length = m, diameter = mm) has a resistance of . What is the resistivity of the material used to make the wire? a. 10 7 m b. 10 7 m c. 10 7 m d. 10 7 m e. 10 7 m L. R= . A. A ( )2. = R = = 10 7 m L 2m 4. A small bulb is rated at W when operated at 125 V. Its resistance (in ohms) is a. b. c. 17. d. 940. e. 2100. P =V2 / R. R = V 2 / P = 1252 / = 2083 . 5. What is the current in the 10- resistor? a. A. b. A. c. A. d. A. e. A.
A resistor of unknown resistance and a 15- Ω resistor are connected across a 20-V battery in such a way that a 2.0 A current is observed in the battery. What is the value of the unknown resistance? a. 75 Ω b. 12 Ω c. 7.5 Ω d. 30 Ω e. 5.0 Ω The equivalent resistance is 20V/2A=10Ω. If one of the known resistors is 15Ω, then
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