PHY Exam #4 (Chapters 23 and 24)

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 Just as water flows from a region of high pressure to a region of low pressure, electric charge flows from a region of A) deep to shallow regions. B) high potential energy to a region of low potential energy. C) high electric pressure to a region of low electric pressure. D) all of the above C Just as in hydraulic circuits there is water pressure, in electric circuits there is A) resistance. B) current. C) voltage. C Just as a sustained flow of water in a hydraulic circuit needs a pump, in electric circuits the flow of charge needs A) current. B) voltage. C) resistance. B To think of electric potential difference we are thinking about A) resistance. B) voltage. C) current. B An ampere is a unit of electric A) voltage. B) current. C) resistance. B Voltage is most similar to A) pressure. B) resistance. C) current. D) all of the above E) none of the above A Electrons flow in a wire when there is A) an imbalance of charges in the wire. B) a difference in potential energy across its ends. C) a potential difference across its ends. D) none of the above C A suitable electric pump in an electric circuit is a A) chemical battery. B) generator. C) both of these D) neither of these C Which statement is correct? A) resistance flows in a circuit B) voltage flows in a circuit C) charge flows in a circuit D) all of the above C It is correct to say that in electric circuits A) flowing charge is current. B) charge flows through a circuit. C) voltage is the ratio of energy per charge. D) voltage is applied across a circuit. E) all of the above E A coulomb of charge flowing in a bulb filament powered by a 6-volt battery is provided with A) 6 watts. B) 6 newtons. C) 6 amperes. D) 6 joules. E) 6 ohms. D The unit of electrical resistance is the A) volt. B) ampere. C) ohm. D) none of the above C The current produced by voltage in a circuit is impeded by A) electric barriers. B) electric resistance. C) closed switches. D) none of the above B If two copper wires of the same length have different thickness, then the thicker wire has A) less resistance. B) more resistance. C) both the same A Heat a copper wire and its electric resistance A) increases. B) remains unchanged. C) decreases. A If you stretch a copper wire so that it is thinner, the resistance between its ends A) increases. B) decreases. C) remains unchanged A Two light bulbs are connected to a battery, one at a time. The bulb that draws more current has the A) higher resistance, but is dimmer. B) lower resistance, but is dimmer. C) lower resistance, and is brightest. D) higher resistance, and is brightest. E) none of the above C When you turn on a lamp, the initial current in its filament is greater at first, rather than a moment later, which indicates A) increased temperature means increased resistance. B) nothing of interest C) a time delay for current attaining its average speed. D) something is faulty. A Ohm’s law tells us that the amount of current produced in a circuit is A) inversely proportional to resistance. B) directly proportional to voltage. C) both of these D) neither of these C Electric resistance in our skin is lowered when our skin is A) moist. B) dry. C) none of the above A Current in a conductor can be increased by A) reducing its resistance. B) increasing the voltage across it. C) both of these D) neither of these C The voltage across a 10-ohm resistor carrying 5 A is A) more than 20 V. B) 5 V. C) 20 V. D) 10 V. E) 15 V. A The resistance of a filament that carries 2 A when a 10-V potential difference across it is A) more than 20 ohms. B) 5 ohms. C) 20 ohms. D) 10 ohms. E) 2 ohms. B Two lamps with different filament thicknesses, and therefore different resistances, are connected in series. Greater current is in the lamp with the A) thin filament. B) same in each C) thick filament. B If an electric toaster rated at 110 V is accidently plugged into a 220-V outlet, the current drawn by the toaster will be A) half its normal value. B) the same as its normal value. C) twice its normal value. D) none of the above C 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 A) 44 ohms. B) 22 ohms. C) 220 ohms. D) 440 ohms. E) none of the above C Direct current is normally produced by a A) battery. B) generator. C) both of these D) neither of these A Alternating current is normally produced by a A) battery. B) generator. C) both of these D) neither of these B Current that is typically 60 hertz is A) alternating current. B) direct current. C) either of these D) neither of these A A capacitor is useful in A) changing dc to ac in a circuit. B) boosting the energy output of a circuit. C) increasing the current in a resistor. D) smoothing pulsed current. E) increasing or decreasing voltage. D An electric diode is useful for A) storing electrical energy. B) voltage modification. C) changing ac to dc. D) boosting voltage. E) limiting current. C For electric current in the home, your power company supplies A) electrons. B) energy. C) both of these D) neither of these B The source of electrons in a simple electric circuit is A) energy stored in the voltage source. B) the voltage source. C) the electrical circuit itself. D) energy released by the voltage source. E) none of the above C The source of electrons that illuminate a common lamp in your home is A) the power company. B) the wires leading to the lamp. C) the electrical outlet. D) atoms in the lamp filament. E) the source voltage. D The source of energy that illuminates a lamp in your home is A) atoms in the bulb filament. B) the electrical outlet. C) the source voltage. D) the power company. E) the wire leads to the lamp D Electrons that are energized to glow in the filament of a common ac lamp are A) electrons already in the filament. B) supplied by a wall outlet, which in turn are supplied by your power company. C) supplied by a wall outlet. D) none of the above A The number of electrons delivered daily to an average American home by an average power utility in the early 21st century was A) 220. B) 110. C) zero. D) billions of billions. E) none of the above C When Eddie Electron experiences an electrical shock, the source of electrons composing the shock is A) whatever electric device being handled. B) Eddie’s body. C) the power plant. D) electric field in the air. E) the ground beneath Eddie’s feet. B The cause of electrical shock is predominantly A) excess voltage. B) excess current. C) reduced resistance. D) none of the above A Electrons flow in an electrical circuit by A) interacting with an established electric field. B) colliding with molecules. C) being bumped by other electrons. D) none of the above A 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) the speed of a sound wave. B) a fraction of a centimeter per second. C) the speed of light. D) many centimeters per second. E) none of the above B The drift speed of electrons that compose current in a flashlight is about A) the speed of sound waves in metal. B) less than 1 cm/s. C) 1000 cm/s. D) the speed of light. E) any of the above under different conditions. B The electric field established by a battery in a dc circuit A) is non-existent. B) acts in one direction. C) increases via the inverse-square law. D) changes magnitude and direction with time. E) none of the above B The electric field established by a generator in an ac circuit A) is non-existent. B) acts in one direction. C) changes magnitude and direction with time. D) increases via the inverse-square law. E) none of the above C Power is defined as the energy expended per unit of time. When translated to electrical terms, power is equal to A) current multiplied by voltage. B) voltage divided by time. C) current multiplied by resistance. D) current divided by time. E) none of the above A In units of measurement, power in watts is equal to A) amperes x volts. B) amperes x ohms. C) volts/second. D) amperes/second. E) none of the above A One joule per coulomb is a unit of A) voltage. B) resistance. C) current. D) energy. E) power. A One kilowatt is a unit of A) voltage. B) current. C) resistance. D) power. E) energy. D One kilowatt-hour is a unit of A) voltage. B) resistance. C) energy. D) current. E) power. C The electric power supplied to a lamp that carries 2 A at 120 V is A) 240 watts. B) 2 watts. C) 60 watts. D) 20 watts. E) 1/6 watts. A A 100-W lamp glows brighter than a 25-W lamp. The electrical resistance of the 100-W lamp is A) the same. B) less. C) greater. B A 100-W lamp glows brighter than a 25-W lamp. The current drawn by the 100-W lamp is A) greater. B) the same. C) less. A When a 12-V battery powers a single 6-ohm lamp, A) 24 joules flow in the lamp each second. B) 12 joules flow in the lamp each second. C) 6 joules flow in the lamp each second. D) 2 joules flow in the lamp each second. A The energy dissipated in a light bulb in a circuit is provided by the A) wires leading to the lamp. B) voltage source. C) lamp filament itself. D) none of the above B When we say an appliance "uses up electricity," we mean A) voltage is lowered. B) electric energy dissipates into heat. C) current disappears. D) electric charges are dissipated. B A 60-W light bulb connected to a 120-V source draws a current of A) 2.0 A. B) 4.0 A. C) 0.25 A. D) 0.5 A. E) more than 4 A. D The power consumed by a device drawing 0.8 A when connected to 120 V is A) 120 W. B) 96 W. C) 15 W. D) 12 W. E) 60 W. B A power line with a resistance of 2 ohms carries a current of 80 A. The power dissipated in the line is A) 320 W. B) 12,800 W. C) 40 W. D) 160 W. E) none of the above B A lamp rated at 120W 120V has a filament resistance of A) 60 ohms. B) 100 ohms. C) 144 ohms. D) 1 ohm. E) none of the above E The power dissipated in a 4-ohm resistor carrying 3 A is A) 18 W. B) 36 W. C) 48 W. D) 7 W. E) need more information B A 60-W and a 100-W light bulb are rated at 120V. Which bulb has a higher resistance? A) 100-W bulb B) 60-W bulb C) both the same. B A 60-W and a 100-W light bulb are connected in series to a 120-V outlet. Which bulb draws more current? A) 60-W bulb B) 100-W bulb C) both the same. C A 60-W and a 100-W light bulb are connected in parallel to a 120-V outlet. Which bulb draws more current? A) 100-W bulb B) 60-W bulb C) both the same. A The current drawn by a 1200-W toaster connected to 120 V is 10 A. The resistance of the toaster coils is A) 12 ohms. B) 18 ohms. C) 6 ohms. E) none of the above A 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? A) more than 5 B) 2 C) 3 D) 4 E) 5 E 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 A) \$11.00. B) \$4.40. C) \$0.44. D) \$1.10. E) none of the above B The brightness of a lamp is directly related to its A) power rating. B) place of manufacture. C) brand. D) all of the above E) none of the above A A lamp rated 23W 120V means that it will deliver 23 W A) whether or not it is connected to 120 V. B) as long as the current is ac. C) when the voltage across it is 120 V. D) none of the above C The amount of current in a CFL rated 23W 120V is about A) more than 5.2A. B) 0.2A. C) 5.2A. B The amount of current in an incandescent bulb rated 75W 120V is about A) 1.2 A. B) 0.4 A. C) 0.6 A. D) more than 1.2 A. C The amount of current in an LED bulb rated 10.5W 120V is A) about 1 A. B) less than 1 A. C) more then 1 A. B Compared with the amount of current in the filament of a lamp, the amount of current in the connecting wires is A) actually more. B) often less. C) definitely less. D) the same. E) incredibly, all of the above D If you wish to keep chicken warm in a shed on a cold night, the best lamp to use is A) an LED lamp. B) a fluorescent lamp. C) an incandescent lamp. D) a CFL lamp. C By convention, the direction of current in a circuit is A) the direction in which positive charge flows. B) from the positive terminal of a source to the negative terminal. C) both of these D) neither of these C In a circuit powered by a battery, charge A) is energized by the battery. B) flows through the battery. C) both of these D) neither of these C When two lamps are connected in series to a battery, the electrical resistance that the battery senses is A) less than the resistance of either lamp. B) more than the resistance of either lamp. C) none of these B 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 When a pair of identical lamps are connected in parallel A) voltage across each is the same. B) current in each is the same. C) power dissipated in each is the same. D) all of the above D On some early automobiles both headlights failed when one bulb burned out. The headlights were likely connected in A) perpendicular. B) parallel. C) haste. D) series. D Modern automobile headlights are connected in A) parallel. B) a perpendicular orientation. C) series. D) none of the above A Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry A) less current. B) more current. C) the same current. A Compared to a single lamp connected to a battery, two lamps connected in parallel to the same battery will carry A) less current. B) the same current. C) more current. C 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 A) sometimes more, sometimes less. B) the same. C) more. D) less. C The safety fuse in an electric circuit is connected to the circuit in A) either series or parallel. B) series. C) parallel. B A circuit breaker often serves the same purpose as a A) battery B) capacitor. C) fuse. D) all of the above E) none of the above C Sometimes the current in lamps is too feeble to produce glowing of the lamp filaments, which occurs when A) too much current is drawn by the battery. B) too many lamps are connected in parallel. C) too many lamps are connected in series. C As more lamps are connected in a series circuit, the overall current in the power source A) decreases. B) stays the same. C) increases. A As more lamps are connected in a parallel circuit, the overall current in the power source A) stays the same. B) decreases. C) increases. C Which is more dangerous, touching a faulty 110-volt light fixture, or a Van de Graaff generator charged to 100,000 volts? A) touching both are about equally dangerous. B) touching the generator C) touching the light fixture C To connect a pair of resistors so their equivalent resistance (the single resistor having their combined value) will increase, connect them in A) parallel. B) series. C) either of these B To connect a pair of resistors so their equivalent resistance (the single resistor having their combined value) will be least, connect them in A) series B) parallel C) either of these B The equivalent resistance of any parallel branch in a circuit is A) usually half the value of the lowest resistor. B) often less than the resistance of the lowest resistor. C) always less than the resistance of the lowest resistor. D) none of the above C The equivalent resistance of any series of resistors in a circuit is A) always less than the resistance of the lowest resistor. B) often less than the resistance of the lowest resistor. C) usually half the value of the lowest resistor. D) none of the above D When a pair of 1-ohm resistors are connected in series, their equivalent (combined) resistance is 2 ohms, and when connected in parallel is A) also 2 ohms. B) none of the above C) ½ ohm. C The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in series is about A) 9 ohms. B) 6 ohms. C) 1 ohm D) 1.8 ohms. B The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in parallel is about A) 1 ohm. B) 0.55 ohm. C) 1.8 ohms. D) 9 ohms. E) 6 ohms. B A 4-ohm and 6-ohm resistor connected in parallel have an equivalent resistance of A) 10 ohms. B) 4 ohms. C) 2.4 ohms. D) 5 ohms. E) 5.5 ohms. C 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 A) 5 ohms. B) greater than 6.7 ohms. C) 1.4 ohms. D) 6.7 ohms. D Three resistors take the shape of a triangle, one resistor in each leg. Resistance in one leg is 4 ohms, 6 ohms in a second leg, and a third leg 10 ohms. Connecting an ohm-meter across the 10-ohm resistor will show the equivalent resistance to be A) 6.7 ohms. B) 5 ohms. C) greater than 6.7 ohms. D) 1.4 ohms. B Magnetic compasses reportedly were first used for navigation by A) Chinese sailors. B) Aristotle. C) Australian aborigines. D) none of the above A The source of all magnetism is A) moving electric charge. B) tiny pieces of iron. C) tiny domains of aligned atoms. D) ferromagnetic materials. E) none of the above A The force that acts between a pair of electrically-charged particles depends on A) magnitude of charge. B) separation distance. C) both of these D) neither of these C The force that acts between a pair of magnetic poles depends on A) separation distance. B) magnetic pole strength. C) both of these D) neither of these C Like kinds of magnetic poles repel while unlike kinds of magnetic poles A) repel also. B) attract. C) may attract or repel. B In general, a common magnet has A) one pole. B) at least two poles. C) only two poles. B Whereas electric charges can be isolated, magnetic poles A) cannot. B) can also. C) gather in clusters. D) none of the above A Refrigerator magnets are typically A) long range B) short range C) none of these B If you break a bar magnet in half you’ll A) have two and a half magnets. B) have two magnets. C) destroy its magnetic properties. D) none of the above B Surrounding every magnet is A) a magnetic field. B) an electric field. C) both of these D) neither of these A Surrounding every moving electron is A) a magnetic field. B) an electric field. C) both of these D) neither of these C Magnetic fields are produced by A) most moving electrical charges. B) all moving electrical charges. C) a tiny fraction of moving electrical charges. B Magnetism is due to the motion of electrons as they A) spin on their axes. B) move around the nucleus. C) both of these D) neither of these C The conventional direction of magnetic field lines outside a magnet are from A) south to north. B) either way C) north to south. C Magnetic field strength about a magnet is strongest where magnetic field lines are A) most curved B) closer together C) straightest D) more spread B An iron rod becomes magnetic when A) opposite ions accumulate at each end. B) its electrons stop moving and point in the same direction. C) the net spins of many of its electrons are aligned. D) its atoms are aligned. E) none of the above C The magnetic fields of a pair of nearby magnets can A) only add. B) add or subtract by vector rules. C) cannot add or subtract. B The end of a compass needle that points to the south pole of a magnet is the A) south pole. B) north pole. C) both of these B A compass needle in a magnetic field A) may experience a pair of torques. B) experiences a pair of torques. C) experiences a torque. A Magnetic domains normally occur in A) silver. B) iron. C) copper. D) all of the above E) none of the above B In the atoms of most materials the fields of individual electrons A) partly align. B) cancel one another. C) completely align. B Wood does not have magnetic properties because it contains no A) magnetic domains. B) iron or other metals. C) moving electrons. D) none of the above A To weaken a bar magnet A) whack it with a hammer. B) drop it on a hard surface. C) put it in hot flames. D) all of the above E) none of the above D An initially unmagnetized iron nail is placed near one of the poles of a magnet. An iron nail is more strongly attracted to the magnet if the nearest pole of the magnet to the nail is the A) south pole of the magnet B) north pole of the magnet C) either of these D) the nail is not attracted to either of these C Several paper clips dangle from the north pole of a magnet. The induced pole in the bottom of the lowermost paper clip is a A) south pole. B) north pole. C) either of these D) neither of these B The shape of a magnetic field surrounding a current-carrying conductor is A) circular. B) radial. C) consistent with the inverse-square law. D) all of these E) neither of these A Magnetic field lines about a current-carrying wire A) circle the wire in closed loops. B) extend radially from the wire. C) both of these D) neither of these A When current reverses direction in a wire, the surrounding magnetic field A) also reverses direction. B) becomes momentarily stronger. C) contracts. D) expands. A When a current-carrying wire is bent into a loop, its magnetic field inside the loop A) cancels. B) weakens. C) becomes concentrated. D) none of the above C As the number of loops in a current-carrying wire is increased, the A) more spread out is the magnetic field. B) stronger the enclosed magnetic field. C) weaker the current. D) greater the back emf. B A beam of electrons passing through a magnetic field experiences maximum deflection if the direction of the beam is A) parallel to the field lines. B) perpendicular to the field lines. C) none of these B A beam of electrons can pass through a magnetic field without being deflected if the direction of the beam is A) perpendicular to the field lines. B) parallel to the field lines. C) none of these B A current-carrying loop of wire experiences no tendency to rotate in a magnetic field when A) field lines pass directly through the loop. B) no field lines pass through the loop. C) none of these A A current-carrying coil of wire is A) a magplane in the making. B) an electromagnet. C) a superconductor. D) a superconducting magnet. B Place an iron rod inside a current-carrying coil of wire and you A) have a superconducting magnet. B) increase the strength of the electromagnet. C) a magplane in the making. B A superconducting magnet uses A) iron cores. B) superconducting coils. C) both of these D) neither of these B Magnet A has twice the magnetic field strength of Magnet B and at a certain distance pulls on magnet B with a force of 100 N. The amount of force that magnet A exerts on magnet B is A) exactly 100 N. B) at or about 50 N. C) need more information A Compared to the huge force that attracts an iron tack to a strong magnet, the force that the tack exerts on the magnet is A) equally huge. B) inversely proportional to their masses. C) relatively small. A Into which stable force field can a proton be placed at rest without being acted upon by a force? A) electric field B) magnetic field C) both of these D) neither of these B The direction of the force exerted on a moving charge in a magnetic field is A) in the direction of the motion. B) opposite its motion. C) at right angles to the direction of the motion. C The force on an electron moving in a magnetic field will be least when its direction is A) the same as the magnetic field direction. B) perpendicular to the magnetic field direction. C) either of these D) neither of these A When an electron passes through the magnetic field of a horseshoe magnet, the electron’s A) speed is increased. B) direction is changed. C) both of these D) neither of these B The force exerted on an electron moving in a magnetic field is maximum when the electron moves A) perpendicular to the magnetic field. B) parallel to the magnetic field. C) either of these D) neither of these A The force a magnetic field exerts on a current-carrying wire is maximum when the wire is oriented A) parallel to the magnetic field. B) perpendicular to the magnetic field. C) either of these D) neither of these B A current-carrying wire in a magnetic field A) may experience a force. B) may be deflected. C) both of these D) neither of these C An electron beam directed through a magnetic field A) may be deflected. B) may experience a force. C) both of these D) neither of these C No net force acts on a loop of wire in a magnetic field when A) no current is in the loop. B) no magnetic field lines pass through the loop. C) both of these D) neither of these C If a magnet produces a force on a current-carrying wire, the wire A) produces a force on the magnet. B) may or may not produce a force on the magnet. C) none of these A A galvanometer indicates A) a flow of electrons. B) electric charge. C) magnetic field strength. D) electric voltage. A A galvanometer can be calibrated to measure A) electric current. B) electric voltage. C) both of these D) none of these C Although a magnet can change the direction of travel of an electron beam, it cannot change its A) speed B) kinetic energy. C) both of these D) neither of these C A beam of singly-charged ions entering a magnetic field with the same speed are swept into circular paths. The wider paths are those of A) the heavier ions. B) the lighter ions. C) neither particularly. A Which force field can increase a moving electron’s speed? A) electric field B) magnetic field C) both of these D) neither of these A Which force field can accelerate an electron? A) electric field B) magnetic field C) both of these D) neither of these C Over geologic history the Earth’s magnetic field A) is unknown. B) has been relatively stable. C) has increased in strength exponentially. D) has reversed direction many times. D Solar winds headed in Earth’s direction are deviated mainly by A) Earth’s radiation belts. B) Earth’s magnetic field. C) the troposphere. D) the upper atmosphere. B The intensity of cosmic rays bombarding the Earth’s surface is most at the A) equator B) mid-latitudes C) poles C An aurora borealis high above the atmosphere is due to A) fountains of high-speed charged particles. B) trapping of charged particles by Earth’s magnetic field. C) disturbances in Earth’s magnetic field. D) all of the above D Cosmic rays penetrate your body when A) safely in your home. B) in mountainous regions. C) outdoors. D) all of the above E) none of the above D Earth’s magnetic field is A) useful to pigeons but not to humans. B) something we’ve learned to live with. C) protective to life on Earth. C Pigeons navigate primarily by A) a keen sense of smell. B) ultra-high-pitched sounds. C) a good memory. D) magnetic sensors in their heads. E) none of the above D Biomagnetism has been detected in A) wasps. B) humans. C) bacteria. D) pigeons. E) all of the above E

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