Ch. 18 and 19 Review Problems 2

Transcription

1 Ch. 18 and 19 Review Problems 2 NAME 1) A device that produces electricity by transforming chemical energy into electrical energy is called a A) generator. B) transformer. C) battery. D) none of the given answers 2) The total amount of charge that passes through a wire's full cross section at any point per unit of time is referred to as A) current. B) electric potential. C) voltage. D) wattage. 3) A coulomb per second is the same as A) a watt. B) an ampere. C) a volt-second. D) a volt per second. 4) The resistance of a wire is A) proportional to its length and its cross-sectional area. B) proportional to its length and inversely proportional to its cross-sectional area. C) inversely proportional to its length and proportional to its cross-sectional area. D) inversely proportional to its length and its cross-sectional area. 5) Consider two copper wires. One has twice the cross-sectional area of the other. How do the resistances of these two wires compare? A) Both wires have the same resistance. B) The thicker wire has half the resistance of the shorter wire. C) The thicker wire has twice the resistance of the shorter wire. D) none of the given answers 6) If the voltage across a circuit of constant resistance is doubled, the power dissipated by that circuit will A) quadruple. B) double. C) decrease to one half. D) decrease to one fourth. 7) If the current flowing through a circuit of constant resistance is doubled, the power dissipated by that circuit will A) quadruple. B) double. C) decrease to one half. D) decrease to one fourth. 8) When resistors are connected in series, A) the same power is dissipated in each one. B) the potential difference across each is the same. C) the current flowing in each is the same. D) More than one of the given answers is true.

2 9) Three identical resistors are connected in series to a battery. If the current of 12 A flows from the battery, how much current flows through any one of the resistors? A) 12 A B) 4 A C) 36 A D) zero 10) When resistors are connected in parallel, we can be certain that A) the same current flows in each one. B) the potential difference across each is the same. C) the power dissipated in each is the same. D) their equivalent resistance is greater than the resistance of any one of the individual resistances. 11) Three identical resistors are connected in parallel to a 12-V battery. What is the voltage of any one of the resistors? A) 36 V B) 12 V C) 4 V D) zero 12) As more resistors are added in parallel to a constant voltage source, the power supplied by the source A) increases. B) decreases. C) does not change. D) increases for a time and then starts to decrease. 13) What current is flowing if 0.67 C of charge pass a point in 0.30 s? 14) A coffee maker, which draws 13.5 A of current, has been left on for 10 min. What is the net number of electrons that have passed through the coffee maker? 15) What potential difference is required to cause 4.00 A to flow through a resistance of 330 Ω?

3 16) A light bulb operating at 110 V draws 1.40 A of current. What is its resistance? 17) What is the resistance of a circular rod 1.0 cm in diameter and 45 m long, if the resistivity is Ω m? 18) Calculate the current through a 10.0-m long 22 gauge (the radius is mm) nichrome wire if it is connected to a 12.0-V battery. (The resistivity of nichrome is Ω m.) 19) 5.00 A is flowing through an 10.0 Ω resistor. How much power is being dissipated? 20) A 110-V hair dryer is rated at 1200 W. What current will it draw? 21) A 200-Ω resistor is rated at 1/4 W. What is the maximum current it can draw?

4 22) A 400-W computer (computer plus monitor) is turned on 8.0 hours per day. If electricity costs 10 cents per kwh, how much does it cost to run the computer annually? 23) A 500-W device is connected to a 120-V ac power source. What is the peak voltage across this device? 24) Four resistors of 12, 3.0, 5.0, and 4.0 Ω are connected in series. A 12-V battery is connected to the combination. What is the current through the battery? 25) Three resistors of 12, 12, and 6.0 Ω are connected in parallel. A 12-V battery is connected to the combination. What is the current through the 6.0-Ω resistor? 26) A 14-A current flows into a series combination of a 3.0-Ω and a 4.0-Ω resistor. What is the voltage drop across the 3.0-Ω resistor? 27) A 22-A current flows into a parallel combination of a 4.0-Ω, 6.0-Ω, and 12-Ω resistor. What current flows through the 4.0-Ω resistor?

5 28) What is the maximum number of 100-W light bulbs you can connect in parallel in a 120-V circuit without tripping a 20-A circuit breaker? 29) Two 4.0-Ω resistors are connected in parallel, and this combination is connected in series with 3.0 Ω. What is the effective resistance of this combination? 30) Two resistors of 5.0 and 9.0 Ω are connected in parallel. A 4.0-Ω resistor is then connected in series with the parallel combination. A 6.0-V battery is then connected to the series-parallel combination. What is the current through the 5.0-Ω resistor? FIGURE ) What is the total resistance of the circuit in Fig. 19-3? A) 950 Ω B) 450 Ω C) 392 Ω D) 257 Ω 32) If E = 100 V, what is the voltage across R5 in Fig. 19-3? A) 19 V B) 40 V C) 75 V D) 77 V