Exam Elementary Physics Chapter 23 Part 1

Chapter 23 ... circuit in which all current travels through each device series circuit short piece of metal that melts if too large a current passes through it fuse occurs when a circuit forms that has a very low resistance short circuit circuit in which there are several different paths for a current parallel circuit automatic switch that opens a circuit when the current reaches some set value circuit breaker circuit that has some resistors in parallel and some in series combination series-parallel circuit value of a single resistor that could replace all resistor in a circuit without changing the current equivalent resistance device used to measure the current in part of a circuit ammeter device used to measure the potential drop across some part of a circuit voltmeter detects small differences in current caused by an extra current path and opens the circuit ground-fault interrupter series circuit used to produce a voltage source from a higher voltage battery voltage divider The current is __ a series circuit. the same everywhere in In an electric circuit, the increase in voltage provided by the generator or other energy source, voltage source is equal to the __ of the voltage drops across the resistors. sum Series resistors R=R1+R2+R3+... Parallel resistors 1/R= 1/R1+1/R2+... In a series circuit, the equivalent resistance is __ any single resistance. larger than If the battery voltage does not change, adding more devices in series __ the current. always decreases Given the voltage of a series circuit, you first calculate __ to find the current through the circuit. the equivalent resistance When appliances are connected in __, each additional appliance placed in operation reduces the equivalent resistance in the circuit and causes more current to flow through the wires, parallel The __ of the metal in a fuse determines the amount of current that will melt the fuse and break the circuit. thickness When a circuit breaker ___, it allows current to flow. closes Ground-fault interrupters can be used as safety devices on circuits in which the current flows along a __ from the power source into the electric outlet and back to the source. single path Electric wiring in homes uses only __ circuits. parallel Low resistance cause the current to be very __ and may result in a short circuit. large An __ measures current. ammeter An ammeter is placed in __ with the resistor if you want to measure the current through a resistor. series So that it will change the current as little as possible, its resistance should be as __ as possible. low A __ measures the voltage drop across a resistor. voltmeter A voltmeter should be connected in __ with a resistor to measure the potential drop across the resistor. parallel So that a voltmeter will change the current as little as possible, its resistance should be as __ as possible. high ch 23 Electrons are made to flow in a wire when there is A. an imbalance of charges in the wire B. more potential energy at one end of the wire than the other C.a potential difference across its ends C. a potential difference across its ends An ampere is a unit of electrical A. pressure B. current C. resistance D. all of these E. none of these B. current a coulomb of charge that passes through a 6-volt battery is given A. 6 joules B. 6 amperes C. 6 ohms D. 6 watts E. 6 newtons A. 6 joules Which statement is correct? A. charge flows in a closed circuit B. voltage flows through an open or a closed circuit C. resistance flows through an open circuit D. current is the primary cause of voltage A. charge flows in a closed circuit Heat a copper wire and its electric resistance A. decreases B. remains unchanged C. increases C. increases The current through a 10-ohm resistor connected to a 120-V power supply is A. 1 A B. 10 A C. 12 A D. 120 A E. none of these C. 12 A When a 10-V battery is connected to a resistor, the current in the resistor is 2 A. What is the resistor's value? A. 2 ohms B. 5 ohms C. 10 ohms D. 20 ohms E. more than 20 ohms B. 5 omhs The source of electrons lighting an incandescent ac light bulb is A. the power company B. electrical outlet C. atoms in the light bulb filament D. the wire leading to the lamp E. the source voltage C. atoms in the light bulb filament in a common dc circuit, electrons move at speeds of A. a fraction of a centimeter per second B. many centimeters per second C. the speed of a sound wave D. the speed of light E. none of these A. a fraction of a centimeter per second The electric power of a lamp that carries 2 A at 120 V is A. 1/6 Watts B. 2 Watts C. 60 Watts D. 20 Watts E. 240 Watts E. 240 Watts When two lamps are connected in parallel to a battery, the electrical resistance that the battery uses is A. more than the resistance of either lamp B. less than the resistance of either lamp C. none of these B. less than the resistance of either lamp When two lamps are connected in series to a battery, the electrical resistance that the battery senses is A. more than the resistance of either lamp B. less than the resistance of either lamp C. none of these A. more than the resistance of either lamp In an electric circuit, the safety fuse is connected to the circuit in A. series B. parallel C. either series or parallel A. series The number of electrons delivered daily to an average American home by an average power utility in the mid 1980's was A. zero B. 110 C. 220 D. billions of billions E. none of these A. zero As more lamps are put into a series circuit, the overall current in the power source A. increases B. decreases C. stays the same B. decreases As more lamps are put into a parallel circuit, the overall current in the power source A. increases B. decreases C. stays the same A. increase Compared to the resistance of two resistors connected in a series, the same two resistors connected in parallel have A. more resistance B. less resistance C. the same resistance B. less resistance When a 60-Watt light bulb is connected to a 120-volt source the current in the light bulb is A. 0.25 A B. 0.5 A C. 2 A D. 4 A E. more than 4 A B. 0.5 A A 4-ohm resistor is connected in parallel with a 6-ohm resistor. This combination produces an equivalent resistance of A. 2.4 ohms B. 4 ohms C. 5 ohms D. 5.5 ohms E. 10 omhs A. 2.4 ohms A power line with a resistance of 2 ohms has a current of 80 A in it. The power dissipated in the line is A. 40 W B. 160 W C. 320 W D. 12,800 W E. none of hese D. 12,800 W Just as a sustained flow of water in a hydraulic circuit needs a pump, in electric circuits the flow of charge needs voltage A coulomb of charge flowing in a bulb filament powered by a 6-volt battery is provided with 6 joules. Heat a copper wire and its electric resistance increases The resistance of a filament that carries 2 A when a 10-V potential difference across it is 5 ohms A capacitor is useful in smoothing pulsed current. The source of energy that illuminates a lamp in your home is the power company The electric field established by a battery in a dc circuit acts in one direction When we say an appliance "uses up electricity," we mean electric energy dissipates into heat. A heater draws 20A when connected to a 110-V line. If the electric power costs 20 cents per kilowatt hour, the cost of running the heater for 10 hours is $4.40. A 100-W lamp glows brighter than a 25-W lamp. The current drawn by the 100-W lamp is greater A 60-W light bulb connected to a 120-V source draws a current of 0.5 A The amount of current in an incandescent bulb rated 75W 120V is about 0.6 A A circuit breaker often serves the same purpose as a fuse As more lamps are connected in a SERIES circuit, the overall current in the power source decreases Compared to a single lamp connected to a battery, two lamps connected in PARALLEL to the same battery will carry more current To connect a pair of resistors so their equivalent resistance (the single resistor having their combined value) will be least, connect them in parallel An ampere is a unit of electric current Voltage is most similar to pressure If two copper wires of the same length have different thickness, then the thicker wire has less resistance Two lamps with different filament thicknesses, and therefore different resistances, are connected in series. Greater current is in the lamp with the same in each An electric diode is useful for changing ac to dc The drift speed of electrons that compose current in a flashlight is about less than 1 cm/s. 단 US$0.99 / 월 The number of electrons delivered daily to an average American home by an average power utility in the early 21st century was zero When a 12-V battery powers a single 6-ohm lamp, 12 joules flow in the lamp each second. A lamp rated at 120W 120V has a filament resistance of none of the above A 60-W and a 100-W light bulb are connected in PARALLEL to a 120-V outlet. Which bulb draws more current? 100-W bulb In units of measurement, power in watts is equal to amperes x volts A lamp rated 23W 120V means that it will deliver 23 W when the voltage across it is 120 V When two lamps are connected in SERIES to a battery, the electrical resistance that the battery senses is more than the resistance of either lamp Connect a pair of lamps in series and current is drawn from the battery. Connect the same lamps in PARALLEL and the current drawn is more When a pair of 1-ohm resistors are connected in series, their equivalent (combined) resistance is 2 ohms, and when connected in PARALLEL is ½ ohm Just as in hydraulic circuits there is water pressure, in electric circuits there is voltage 단 US$0.99 / 월 A suitable electric pump in an electric circuit is a both of these The current produced by voltage in a circuit is impeded by electric resistance Electric resistance in our skin is lowered when our skin is moist Alternating current is normally produced by a generator The current drawn by a 1200-W toaster connected to 120 V is 10 A. The resistance of the toaster coils is 12 ohms A power line with a resistance of 2 ohms carries a current of 80 A. The power dissipated in the line is 12,800 W The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in series is about 6 ohms The source of electrons that illuminate a common lamp in your home is atoms in the lamp filament When two lamps are connected in PARALLEL to a battery, the electrical resistance that the battery senses is less than the resistance of either lamp. If you stretch a copper wire so that it is thinner, the resistance between its ends increases Current in a conductor can be increased by both of these Current that is typically 60 hertz is alternating current Electrons flow in an electrical circuit by interacting with an established electric field The power dissipated in a 4-ohm resistor carrying 3 A is 36 W A 60-W and a 100-W light bulb are connected in SERIES to a 120-V outlet. Which bulb draws more current? both the same If you wish to keep chicken warm in a shed on a cold night, the best lamp to use is an incandescent lamp By convention, the direction of current in a circuit is both of these The equivalent resistance of any series of resistors in a circuit is none of the above To think of electric potential difference we are thinking about voltage Electrons flow in a wire when there is a potential difference across its ends. The unit of electrical resistance is the ohm The cause of electrical shock is predominantly excess voltage One kilowatt-hour is a unit of energy Power is defined as the energy expended per unit of time. When translated to electrical terms, power is equal to current multiplied by voltage. Three 10-ohm resistors take the shape of a triangle, one resistor in each leg. Connecting an ohm-meter across any two points of the triangle will show the equivalent resistance to be 6.7 ohms When a pair of identical lamps are connected in PARALLEL all of the above Modern automobile headlights are connected in parallel The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in parallel is about 0.06 ohm If an electric toaster rated at 110 V is accidently plugged into a 220-V outlet, the current drawn by the toaster will be twice its normal value Direct current is normally produced by a battery When Eddie Electron experiences an electrical shock, the source of electrons composing the shock is Eddie's body The electric field established by a generator in an ac circuit changes magnitude and direction with time An electric heater is rated 300W 110V. The safety fuse in the circuit can withstand 15 A of current. How many heaters can be safely operated in the circuit? 5 The power consumed by a device drawing 0.8 A when connected to 120 V is 96W A 4-ohm and 6-ohm resistor connected in parallel have an equivalent resistance of 2.4 ohms Which statement is correct? charge flows in a circuit The current in two identical light bulbs connected in series is 0.25 A. The voltage across both bulbs is 110 V. The resistance of a single light bulb is 220 ohms For electric current in the home, your power company supplies energy One kilowatt is a unit of power The energy dissipated in a light bulb in a circuit is provided by the voltage source Which is more dangerous, touching a faulty 110-volt light fixture, or a Van de Graaff generator charged to 100,000 volts? Which is more dangerous, touching a faulty 110-volt light fixture, or a Van de Graaff generator charged to 100,000 volts? As more lamps are connected in a PARALLEL circuit, the overall current in the power source increases A 100-W lamp glows brighter than a 25-W lamp. The electrical resistance of the 100-W lamp is less Although electrons in metal move in haphazard directions at many times the speed of sound, the drift speed of electrons that compose electric current is a fraction of a centimeter per second The source of electrons in a simple electric circuit is the electrical circuit itself. On some early automobiles both headlights failed when one bulb burned out. The headlights were likely connected in series Just as water flows from a region of high pressure to a region of low pressure, electric charge flows from a region of high electric pressure to a region of low electric pressure. Ohm's law tells us that the amount of current produced in a circuit is both of these The brightness of a lamp is directly related to its power rating. In a circuit powered by a battery, charge both of these To connect a pair of resistors so their equivalent resistance (the single resistor having their combined value) will increase, connect them in series Compared to a single lamp connected to a battery, two identical lamps connected in SERIES to the same battery will carry less current One joule per coulomb is a unit of voltage Just as in hydraulic circuits there is water pressure, in electric circuits there is voltage The electric power supplied to a lamp that carries 2 A at 120 V is 240 watts The current drawn by a 1200-W toaster connected to 120 V is 10 A. The resistance of the toaster coils is 12 ohms The safety fuse in an electric circuit is connected to the circuit in series 2) An ampere is a unit of electrical A) pressure. B) current. C) resistance. D) all of these E) none of these B 5) Which statement is correct? A) Charge flows in a closed circuit. B) Voltage flows through an open or a closed circuit. C) Resistance flows though an open circuit. D) Current is the primary cause of voltage. A 11) The current through a 10-ohm resistor connected to a 120-V power supply is A) 1 A. B) 10 A. C) 12 A. D) 120 A. E) none of these C 12) A 10-ohm resistor has a 5-A current in it. What is the voltage across the resistor? A) 5 V B) 10 V C) 15 V D) 20 V E) more than 20 V E 13) When a 10-V battery is connected to a resistor, the current in the resistor is 2 A. What is the resistor's value? A) 2 ohms B) 5 ohms C) 10 ohms D) 20 ohms E) more than 20 ohms B 17) In a common dc circuit, electrons move at speeds of A) a fraction of a centimeter per second. B) many centimeters per second. C) the speed of a sound wave. D) the speed of light. E) none of these A 18) When a light switch is turned on in a dc circuit, the average speed of electrons in the lamp is A) the speed of sound waves in metal. B) the speed of light. C) 1000 cm/s. D) less than 1 cm/s. E) dependent on how quickly each electron bumps into the next electron. D 20) The electric power of a lamp that carries 2 A at 120 V is A) 1/6 watts. B) 2 watts. C) 60 watts. D) 20 watts. E) 240 watts. E 21)When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is A)more than the resistance of either lamp. B)less than the resistance of either lamp. C)none of these B 22) When two lamps are connected in series to a battery, the electrical resistance that the battery senses is A)more than the resistance of either lamp. B)less than the resistance of either lamp. C)none of these A 23) On some early automobiles both headlights went out when one bulb burned out. The headlights must have been connected in A)parallel. B)perpendicular. C)series. D)haste. C 24) Modern automobile headlights are connected in A) parallel. B) perpendicular. C) series. D) none of these A 26) A 100-Watt lamp glows brighter than a 25-Watt lamp. The electrical resistance of the 100-Watt lamp must be A) less. B) greater. C) the same. A 27) In an electric circuit, the safety fuse or circuit breaker is connected to the circuit in A) series. B) parallel. C) either series or parallel. A 28) When a pair of 1-ohm resistors are connected in series, their combined resistance is A) 1 ohm, and when connected in parallel, 2 ohms. B) 2 ohms, and when in parallel, 1 ohm. C) 1/2 ohm, and when in parallel, 2 ohms. D) 2 ohms, and when in parallel, 1/2 ohm. E) none of these D 29) A circuit breaker often serves the same purpose as a A) battery B) fuse. C) capacitor. D) All of the above choices are correct. E) None of the above choices are correct. B 33) In a simple circuit containing a bulb, energy is given to the moving charges by A) the bulb. B) the wires. C) a generator. D) none of these C 40) As more lamps are put into a series circuit, the overall current in the power source A) increases. B) decreases. C) stays the same. B 41) As more lamps are put into a parallel circuit, the overall current in the power source A) increases. B) decreases. C) stays the same. A 43) When we say an appliance "uses up electricity," we really are saying that A) current disappears. B) electric charges are dissipated. C) the main power supply voltage is lowered. D) electrons are taken out of the circuit and put somewhere else. E) electron kinetic energy is changed into heat E 44) Compared to the resistance of two resistors connected in series, the same two resistors connected in parallel have A) more resistance. B) less resistance. C) the same resistance. B 45) If you plug an electric toaster rated at 110 V into a 220-V outlet, the current in the toaster will be about A) half what it should be. B) the same as if it were plugged into 110 V. C) more than twice what it should be. D) twice what it should be. D 46) When a 60-watt light bulb is connected to a 120-volt source the current in the light bulb is A)0.25 A. B)0.5 A. C) 2 A. D) 4 A. E)more than 4 A. B 47) If 0.8 A of current flow through a light bulb connected to a 120 V outlet, the power consumed is A) 12 W. B) 15 W. C) 60 W. D) 96 W. E) 120 W. D 48) The headlights, radio, and defroster fan in an automobile are connected in A) series with a switch for each. B) parallel with a switch for each. C) series without separate switches. D) parallel without separate switches. B 49) A 4-ohm resistor is connected in parallel with a 6-ohm resistor. This combination produces an equivalent resistance of A) 2.4 ohms. B) 4 ohms. C) 5 ohms. D) 5.5 ohms. E) 10 ohms. A 50) The power dissipated in a 4-ohm resistor carrying 3 A is A) 7 W. B) 18 W. C) 36 W. D) 48 W. E) not enough information to say C 51) Which is more dangerous, touching a faulty 110-volt light fixture, or a Van de Graaff generator charged to 100,000 volts? A) touching the light fixture B)touching the generator C)Touching both are about equally dangerous. A 52) A 60-W light bulb and a 100-W light bulb are each rated at 120 V. Which light bulb has a larger resistance? A) the 60-W bulb B) the 100-W bulb C) Both have the same resistance. A 53) A 60-W light bulb and a 100-W light bulb are connected in series to a 120 V outlet. Which light bulb has more current in it? A) the 60-W bulb B) the 100-W bulb C) Both have the same current. C Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry A) more current. B) less current. C) the same current. B 56) Compared to a single lamp connected to a battery, two lamps connected in parallel to the same battery will carry A) more current. B) less current. C) the same current. A 57) An electric heater is rated at 300 W when used in a 110-V circuit. The safety fuse in the circuit can handle 15 A of current. How many heaters can be safely operated in the circuit? A)2 B)3 C)4 D)5 E)more than 5 D 58) A heater uses 20 A when used in a 110-V line. If electric power costs 10 cents per kilowatt hour, the cost of running the heater for 10 hours is A)$0.22. B)$0.55. C)$2.20. D)$5.50. E)none of these C 59)The current through two identical light bulbs connected in series is 0.25 A. The voltage across both bulbs is 110 V. The resistance of a single light bulb is A) 22 ohms. B) 44 ohms. C) 220 ohms. D) 440 ohms. E) none of these C 60) A power line with a resistance of 2 ohms has a current of 80 A in it. The power dissipated in the line is A) 40 W. B) 160 W. C) 320 W. D) 12,800 W. E) none of these D 61) What is the resistance of a 120-W incandescent lamp connected to a 120-V power supply? A) 1 ohm B) 60 ohms C) 100 ohms D) 144 ohms E) none of these E 62) Compared to the amount of electric current in the filament of a lamp, the amount of current in the connecting wire is A) definitely less. B) often less. C) actually more. D) the same. E) incredibly, all of these. D 63) Connect a pair of lamps in series and you draw current from the connected battery. Connect the same lamps in parallel and you draw A) the same current. B) more current. C) less current. D) sometimes more, sometimes less. B