AP Physics B Ch 18 and 19 Ohm's Law and Circuits

Name: Period: Date: AP Physics B Ch 18 and 19 Ohm's Law and Circuits MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A device that produces electricity by transforming chemical energy into electrical energy is called a A) battery. B) generator. C) transformer. D) none of the given answers 1) 2) A car battery A) has an emf of 6 V consisting of three 2-V cells connected in series. B) has an emf of 6 V consisting of one 6-V cell. C) has an emf of 6 V consisting of three 2-V cells connected in parallel. D) has an emf of 12 V consisting of six 2-V cells connected in series. 2) 3) 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) voltage. C) electric potential. D) wattage. 3) 4) The direction of convention current is taken to be the direction that A) positive charges would flow. B) negative charges would flow. 4) 5) A coulomb per second is the same as A) an ampere. B) a watt. C) a volt-second. D) a volt per second. 5) 6) Car batteries are rated in "amp-hours." This is a measure of their A) power. B) emf. C) current. D) charge. 6) 7) The resistance of a wire is defined as A) (current)*(voltage). B) (voltage)/(current). C) (current)/(voltage). D) none of the given answers 7) 8) What is 1! equivalent to? A) 1 J/s B) 1 V/A C) 1 W/A D) 1 V A 8) 9) The resistance of a wire is A) proportional to its length and inversely proportional to its cross-sectional area. B) inversely proportional to its length and proportional to its cross-sectional area. C) proportional to its length and its cross-sectional area. D) inversely proportional to its length and its cross-sectional area. 9) 1

10) The resistivity of a wire depends on A) its cross-sectional area. B) its length. C) the material out of which it is composed. 10) 11) Which conducting material has the lowest resistivity value? A) copper B) aluminum C) silver D) gold 11) 12) Consider two copper wires. One has twice the length of the other. How do the resistivities of these two wires compare? A) The longer wire has twice the resistivity of the shorter wire. B) The longer wire has four times the resistivity of the shorter wire. C) Both wires have the same resistivity. D) none of the given answers 12) 13) Consider two copper wires. One has twice the length of the other. How do the resistances of these two wires compare? A) The longer wire has twice the resistance of the shorter wire. B) Both wires have the same resistance. C) The longer wire has half the resistance of the shorter wire. D) none of the given answers 13) 14) Consider two copper wires. One has twice the cross-sectional area of the other. How do the resistances of these two wires compare? A) The thicker wire has half the resistance of the shorter wire. B) The thicker wire has twice the resistance of the shorter wire. C) Both wires have the same resistance. D) none of the given answers 14) 15) Consider two copper wires. One has twice the length and twice the cross-sectional area of the other. How do the resistances of these two wires compare? A) The longer wire has twice the resistance of the shorter wire. B) Both wires have the same resistance. C) The longer wire has four times the resistance of the shorter wire. D) none of the given answers 15) 16) The length of a wire is doubled and the radius is doubled. By what factor does the resistance change? A) quarter as large B) half as large C) twice as large D) four times as large 16) 17) How much more resistance does a 1.0 cm diameter rod have compared to a 2.0 cm diameter rod of the same length and made of the same material? A) 400% B) 100% C) 75% D) 300% 17) 2

18) The resistivity of most common metals A) varies randomly as the temperature increases. B) increases as the temperature increases. C) decreases as the temperature increases. D) remains constant over wide temperature ranges. 18) 19) Negative temperature coefficients of resistivity A) exist in semiconductors. B) do not exist. C) exist in conductors. D) exist in superconductors. 19) 20) What is 1 W equivalent to? A) 1 V A B) 1 V/A C) 1 V/! D) 1! A 20) 21) A kilowatt-hour is equivalent to A) 3,600,000 J. B) 3,600,000 J/s. C) 1000 W. D) 3600 s. 21) 22) If the resistance in a constant voltage circuit is doubled, the power dissipated by that circuit will A) increase by a factor of two. B) decrease to one-half its original value. C) decrease to one-fourth its original value. D) increase by a factor of four. 22) 23) If the voltage across a circuit of constant resistance is doubled, the power dissipated by that circuit will A) quadruple. B) decrease to one half. C) decrease to one fourth. D) double. 23) 24) If the resistance in a circuit with constant current flowing is doubled, the power dissipated by that circuit will A) quadruple. B) decrease to one half. C) double. D) decrease to one fourth. 24) 25) If the current flowing through a circuit of constant resistance is doubled, the power dissipated by that circuit will A) decrease to one half. B) quadruple. C) decrease to one fourth. D) double. 25) 26) During a power demand, the voltage output is reduced by 5.0%. By what percentage is the power on a resistor affected? A) 90% less B) 5.0% less C) 2.5% less D) 10% less 26) 27) A current that is sinusoidal with respect to time is referred to as A) a direct current. B) an alternating current. 27) 28) Consider two copper wires each carrying a current of 3.0 A. One wire has twice the diameter of the other. The ratio of the drift velocity in the smaller diameter wire to that in the larger diameter wire is A) 2:1. B) 1:4. C) 1:2. D) 4:1. 28) 3

29) Materials in which the resistivity becomes essentially zero at very low temperatures are referred to as A) semiconductors. B) conductors. C) insulators. D) superconductors. 29) 30) The potential difference between the terminals of a battery, when no current flows to an external circuit, is referred to as the A) emf. B) terminal voltage. 30) 31) The potential difference between the terminals of a battery, when current flows to an external circuit, is referred to as the A) emf. B) terminal voltage. 31) 32) When two or more resistors are connected in series to a battery A) the same current flows through each resistor. B) the total voltage across the combination is the algebraic sum of the voltages across the individual resistors. C) the equivalent resistance of the combination is equal to the sum of the resistances of each resistor. 32) 33) When resistors are connected in series, A) the potential difference across each is the same. B) the same power is dissipated in each one. C) the current flowing in each is the same. D) More than one of the given answers is true. 33) 34) 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) zero B) 12 A C) 36 A D) 4 A 34) 35) Three identical resistors are connected in series to a 12-V battery. What is the voltage across any one of the resistors? A) 4 V B) zero C) 36 V D) 12 V 35) 36) You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in the normal way, you devise a circuit that places them in series across normal household voltage. Which statement is correct? A) The 50-W bulb glows more brightly than the 100-W bulb. B) Both bulbs glow at the same reduced brightness. C) The 100-W bulb glows brighter than the 50-W bulb. D) Both bulbs glow at the same increased brightness. 36) 37) As more resistors are added in series to a constant voltage source, the power supplied by the source A) increases. B) does not change. C) decreases. D) increases for a time and then starts to decrease. 37) 4

38) When two or more resistors are connected in parallel to a battery, A) the voltage across each resistor is the same. B) the equivalent resistance of the combination is less than the resistance of any one of the resistors. C) the total current flowing from the battery equals the sum of the currents flowing through each resistor. 38) 39) When resistors are connected in parallel, we can be certain that A) their equivalent resistance is greater than the resistance of any one of the individual resistances. B) the power dissipated in each is the same. C) the same current flows in each one. D) the potential difference across each is the same. 39) 40) 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) zero C) 12 V D) 4 V 40) 41) Three identical resistors are connected in parallel to a battery. If the current of 12 A flows from the battery, how much current flows through any one of the resistors? A) 36 A B) 4 A C) 12 A D) zero 41) 42) The lamps in a string of Christmas tree lights are connected in parallel. What happens if one lamp burns out? (Assume negligible resistance in the wires leading to the lamps.) A) The other lamps get brighter equally. B) The other lamps get dimmer, but some get dimmer than others. C) The other lamps get dimmer equally. D) The brightness of the lamps will not change appreciably. E) The other lamps get brighter, but some get brighter than others. 42) 43) As more resistors are added in parallel to a constant voltage source, the power supplied by the source A) increases. B) increases for a time and then starts to decrease. C) decreases. D) does not change. 43) 44) Consider three identical resistors, each of resistance R. The maximum power each can dissipate is P. Two of the resistors are connected in series, and a third is connected in parallel with these two. What is the maximum power this network can dissipate? A) 3P B) 2P C) 2P/3 D) 3P/2 44) ESSAY. Write your answer in the space provided or on a separate sheet of paper. 45) State Kirchhoff's junction rule. 46) State Kirchhoff's loop rule. 5

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 47) Kirchhoff's loop rule is an example of A) conservation of momentum. B) conservation of charge. C) conservation of energy. D) none of the given answers 47) 48) Kirchhoff's junction rule is an example of A) conservation of charge. B) conservation of momentum. C) conservation of energy. D) none of the given answers 48) 49) Which of the equations here is valid for the circuit shown? 49) FIGURE 19-1 A) -2 - I1-2I2 = 0 B) 6 - I1-2I2 = 0 C) 2-2I1-2I2-4I3 = 0 D) 2 - I1-2I2 = 0 E) 4 - I1 + 4I3 = 0 50) If you connect two identical storage batteries together in series ("+" to "-" to "+" to "-"), and place them in a circuit, the combination will provide A) zero volts. B) twice the voltage, and the same current will flow through each. C) the same voltage, and different currents will flow through each. D) twice the voltage, and different currents will flow through each. 50) 51) If you connect two identical storage batteries together in series ("+" to "-" to "-" to "+"), and place them in a circuit, the combination will provide A) zero volts. B) twice the voltage, and the same current will flow through each. C) the same voltage, and different currents will flow through each. D) twice the voltage, and different currents will flow through each. 51) 6

52) If you connect two identical storage batteries together in parallel, and place them in a circuit, the combination will provide A) half the voltage and half the total charge that one battery would. B) the same voltage and twice the total charge that one battery would. C) twice the voltage and twice the total charge that one battery would. D) twice the voltage and the same total charge that one battery would. 52) 53) When two or more capacitors are connected in series to a battery, A) each capacitor carries the same amount of charge. B) the total voltage across the combination is the algebraic sum of the voltages across the individual capacitors. C) the equivalent capacitance of the combination is less than the capacitance of any of the capacitors. 53) 54) As more and more capacitors are connected in series, the equivalent capacitance of the combination increases. A) always true B) never true C) Sometimes true; it depends on the voltage of the battery to which the combination is connected. D) Sometimes true; it goes up only if the next capacitor is larger than the average of the existing combination. 54) 55) Three identical capacitors are connected in series to a battery. If a total charge of Q flows from the battery, how much charge does each capacitor carry? A) Q/3 B) 3Q C) Q/9 D) Q 55) 56) When two or more capacitors are connected in parallel to a battery, A) the voltage across each capacitor is the same. B) the equivalent capacitance of the combination is less than the capacitance of any one of the capacitors. C) each capacitor carries the same amount of charge. 56) 57) As more and more capacitors are connected in parallel, the equivalent capacitance of the combination increases. A) never true B) always true C) Sometimes true; it depends on the voltage of the battery to which the combination is connected. D) Sometimes true; it goes up only if the next capacitor is larger than the average of the existing combination. 57) 58) Three identical capacitors are connected in parallel to a battery. If a total charge of Q flows from the battery, how much charge does each capacitor carry? A) Q B) Q/3 C) Q/9 D) 3Q 58) 7

59) What is the unit for the quantity RC? A) meters B) ohms C) seconds D) volt-ampere/ohm 59) 60) A resistor and a capacitor are connected in series to an ideal battery of constant terminal voltage. At the moment contact is made with the battery, the voltage across the capacitor is A) less than the battery's terminal voltage, but greater than zero. B) zero. C) greater than the battery's terminal voltage. D) equal to the battery's terminal voltage. 60) 61) A resistor and a capacitor are connected in series to an ideal battery of constant terminal voltage. At the moment contact is made with the battery, the voltage across the resistor is A) equal to the battery's terminal voltage. B) greater than the battery's terminal voltage. C) less than the battery's terminal voltage, but greater than zero. D) zero. 61) 62) A resistor and a capacitor are connected in series to an ideal battery of constant terminal voltage. When this system reaches its steady-state, the voltage across the resistor is A) greater than the battery's terminal voltage. B) less than the battery's terminal voltage, but greater than zero. C) zero. D) equal to the battery's terminal voltage. 62) 63) An ideal ammeter should A) introduce a very small series resistance into the circuit whose current is to be measured. B) consist of a galvanometer in series with a large resistor. C) introduce a very large series resistance into the circuit whose current is to be measured. D) have a high coil resistance. 63) 64) A galvanometer can be converted to an ammeter by the addition of a A) large resistance in parallel. B) large resistance in series. C) small resistance in parallel. D) small resistance in series. 64) 65) A current reading is obtained by properly placing an ammeter in a circuit consisting of one resistor and one battery. As a result, A) the current flowing in the circuit increases. B) the voltage drop across the resistor increases. C) the current flowing in the circuit does not change. D) the current flowing in the circuit decreases. 65) 66) Decreasing the resistance of an ammeter's shunt resistance A) allows it to measure a larger current at full scale deflection. B) converts it to a voltmeter. C) enables more current to pass directly through the galvanometer. D) allows it to measure a smaller current at full scale deflection. 66) 8

67) In order to construct a voltmeter from a galvanometer, one normally would A) use a very small shunt resistor. B) use a very small series resistor. C) use a very large series resistor. D) use a very large shunt resistor. 67) 68) Increasing the resistance of a voltmeter's series resistance A) enables more current to pass through the meter movement at full-scale deflection. B) allows it to measure a larger voltage at full-scale deflection. C) converts it to an ammeter. D) allows it to measure a smaller voltage at full-scale deflection. 68) 69) A voltage reading is obtained by placing a voltmeter across a resistor. What happens to the total current flowing in the circuit as a result of this action? A) The current increases. B) The current increases if the meter's internal resistance is less than the original resistance in the circuit and decreases if its internal resistance is greater than the circuit's original resistance. C) The current decreases. D) The current does not change. 69) 70) An unknown resistor is wired in series with an ammeter, and a voltmeter is placed in parallel across both the resistor and the ammeter. This network is then placed across a battery. If one computes the value of the resistance by dividing the voltmeter reading by the ammeter reading, the value obtained A) is the true resistance. B) is greater than the true resistance. C) is less than the true resistance. D) could be any of the given answers. It depends on other factors. 70) 71) An unknown resistor is wired in series with an ammeter, and a voltmeter is placed in parallel across the resistor only. This network is then connected to a battery. If one computes the value of the resistance by dividing the voltmeter reading by the ammeter reading, the value obtained A) is the true resistance. B) is less than the true resistance. C) is greater than the true resistance. D) could be any of the given answers. It depends on other factors. 71) 9