Physics exam 3 – Flashcards
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Magnetic domains are composed of clustered _______. a) crystals of iron ions b) aligned iron atoms c) electrically charged iron atoms d) iron atoms in random directions
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b
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The magnetic field about a straight length of current-carrying wire is _______. a) similar to the shape of an electric field about a charged wire b) in accord with the inverse square law c) aligned from north to south poles in the wire d) circular in shape
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d
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What kinds of appliances work on the principle of deflection of a current-carrying wire in a magnetic field? a) electric motor b) both an electric generator and an electric motor c) electric generator
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a
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What happens when a switch is closed in a circuit that contains a battery and a wire that is placed between the poles of a magnet? a)The wire will either bend up or down between the poles of the magnet due to the force of the magnetic field. b) nothing happens. The wire will stay where it is c) The wire will fall under the force of gravity
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a
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What happens to the shape of a wire that is part of a circuit with a battery when the switch is closed and the battery voltage is increased? a) the wire bends more than it did before b) the wire becomes more horizontal; that is, the wire bends less c) the shape does not change
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a
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What happens to the shape of a wire that is part of a circuit with a battery when the switch is closed and the direction of the current is reversed in the wire? a) the wire will bend more, but in the same direction b) the wire will bend less, but in the same direction c) the wire will bend the same amount but in the opposite direction d) the shape of the wire will not change
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c
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If a compass is moved from the northern hemisphere to the southern hemisphere, its magnetic needle will change direction a) by 180 degrees b) hardly at all c) by 90 degrees d) depending on where the measurement is taken e) none of these
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b
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An iron rod becomes magnetic when a) positive ions accumulate at one end and negative ions at the other end b) the net spins of its electrons are in the same direction c) its atoms are aligned having plus charges on one side and negative charges on the other d) its electrons stop moving and point in the same direction e) none of these
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b
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If a steady magnetic field exerts a force on a moving charge, that force is directed a) in the direction of the motion b) at right angles to the direction of the motion c) opposite the motion
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b
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Moving electric charges will interact with a) an electric field or a magnetic field b) only a magnetic field c) only an electric field d) none of these
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a
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the source of all magnetism is a) tiny pieces of iron b) tiny domains of aligned atoms c) moving electric charge d) ferromagnetic materials d) none of these
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c
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Magnetic field lines about a current-carrying wire a) circle the wire in closed loops b) extend radially from the wire c) choices a and b are both correct d) none of the above choices are correct
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a
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magnetic domains normally occur in a) iron b) copper c) silver d) all of these e) none of these
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a
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The field surrounding every moving electron is a) always electric but never magnetic b) always magnetic but never electric c) always both electric and magnetic d) sometimes magnetic and sometimes electric e) none of the above
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c
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an iron nail is more strongly attracted to the a) south pole of a magnet b) north or south pole c) north pole of a magnet
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b
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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) north pole b) north or south pole c) south pole
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a
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A proton moves in a circular path perpendicular to a constant magnetic field. If the field strength of the magnet is increased, does the diameter of the circular path increase, decrease, or remain the same? a) the diameter of the circular path increases b) the diameter of the circular path decreases c) the diameter of the circular path remains the same
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b
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If a steady magnetic field exerts a force on a moving charge, that force is directed a) opposite the direction of the field b) at right angles to the direction of the field c) in the direction of the field
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b
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Like kinds of magnetic poles repel while unlike kinds of magnetic poles a) attract b) repel also c) may attract or repel
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a
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The force on an electron moving in a magnetic field will be the largest when its direction is a) at an angle other than 90 degrees to the magnetic field direction b) perpendicular to the magnetic field direction c) exactly opposite to the magnetic field direction d) the same as the magnetic field direction e) none of these
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b
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magnetism is due to the motion of electrons as they a) spin on their axes b) move around the nucleus c) choices a and b are correct d) none of the above are correct
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c
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Which pole of a compass needle points to a south pole of a magnet? a) south pole b) north pole c) both of these
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b
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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) more information is needed
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a
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Outside a magnet, magnetic field lines are conventionally drawn from a) south to north b) north to south c) either way
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b
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An electron is shot through a spot somewhere between the ends of a horseshoe magnet. The electron a) is attracted to one of the poles, and repelled by the other b) is unaffected by the field c) direction is changed d) is repelled by both poles, and therefore is turned back e) speed is increased
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c
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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) relatively small b) equally huge c) more information is needed
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b
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If the speed of the magnet is doubled, the induced voltage is ________ .
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twice as great
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What happens when a wire is held between the poles of a magnet? a) nothing happens b) the wire becomes magnetized c) a voltage is generated in the wire
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a
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What happens when a wire is moved between the poles of a magnet? a) the wire becomes magnetized b) a voltage is generated in the wire c) nothing happens
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b
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What happens to the induced voltage if you increase the number of loops in the wire? a) the induced voltage increases b) the induced voltage stays the same c) the induced voltage decrease
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a
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How do you induce a voltage in a conducting loop of wire? a) hold the loop outside a magnetic field b) change the magnetic field in the loop c) hold the loop in a magnetic field
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b
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Faraday's law states that induced voltage in a loop of wire depends on the rate at which _______. a) voltage changes b) a magnetic is thrust into the loop c) current is made to oscillate within the loop d) a magnetic field in the loop changes
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d
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What transforms from one coil to another in a transformer is _______. a) mainly current b) mainly voltage c) power d) electricity
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c
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What ultimately transfers from one location to another in electromagnetic induction is _______. a) electric fields b) light c) energy d) force
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c
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If the primary of a transformer were connected to a dc power source, the transformer would have a voltage output a) at a higher efficiency then with an ac source b) only while being connected or disconnected c) the same d) that is also dc e) none of these
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b
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The voltage across the input terminals of a transformer is 110 V. The primary has 50 loops and the secondary has 25 loops. The voltage the transformer puts out is a) 220 V b) 55 V c) 25 V d) 110 V e) none of these
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b
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Metal detectors, like the ones used at airports, are activated by a) alternating current b) magnetic fields c) electric fields d) electromagnetic induction
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d
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A certain transformer doubles input voltage. If the primary coil has 10 A of current, then the current in the secondary coil is a) 2 A b) 5 A c) 25 A d) 10 A e) none of the above
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b
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A step-up transformer has a ratio of one to ten. Neglecting slight losses, if 100 W of power go into the primary coil, the power coming from the secondary coil is a) 100 W b) 1000 W c) 1 W d) 10 W e) none of these
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a
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A step-up transformer increases a) energy b) power c) both power and energy d) neither power of energy
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d
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Compared to the primary voltage, the secondary voltage may be a) the same b) the same or smaller, but not larger c) larger d) smaller e) larger, smaller, or the same
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e
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Transformers use ac so there will be the required a) change in magnetic field for operation b) magnetic field intensities c) voltage for transformation d) change in input current e) transfer of energy from coil to coil
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a
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The primary of a transformer is the coil connected to a) the power line b) the internet c) the load d) none of these
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a
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An electric motor is very similar to a) an automobile b) an electric generator c) a radio receiver d) none of the above choices are correct
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b
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A device that transforms mechanical energy into electrical energy is a a) magnet b) motor c) generator d) transformer e) none of these
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c
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Voltage can be induced in a wire by a) moving a magnet near the wire b) changing the current in a nearby wire c) moving the wire near a magnet d) choices a, b, c are all true e) none of the above choices are true
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d
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When a bar magnet is thrust into a coil of copper wire, the coil tends to a) attract the magnet as it enters b) repel the magnet as it enters c) both of these d) neither of these
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b
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Thrust a magnet into a coil of wire and the coil a) has a current in it b) becomes an electromagnet c) both of these d) neither of these
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c
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When there is a change in the magnetic field in a closed loop of wire a) electromagnetic induction occurs b) a current is created in the loop of wire c) a voltage is induced in the wire d) all of these e) none of these
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d
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Which travels faster through a vacuum - an infrared ray or a gamma ray? a) an infrared ray b) a gamma ray c) both travel at the same speed
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c
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Electromagnetic waves are composed of _______. a) electric and magnetic fields b) vibrating light vectors c) light waves d) perpendicular longitudinal waves
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a
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The smallest portion of the electromagnetic spectrum is _______. a) none in particular, as all make up equal portions of the spectrum b) visible light c) radio d) infrared
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b
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The electromagnetic waves having the highest speed in free space are _______. a) light waves b) gamma rays c) radio waves d) none in particular, as gamma, radio, and light waves have the same speed
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d
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The electromagnetic radiation mostly absorbed in ordinary glass is _______. a) red light b) yellow-green light c) translucent light d) ultraviolet
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d
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Strictly speaking, the light that meets and passes through a pane of window glass _______. a) is the same light that emerges b) is not the same light that emerges c) gains energy d) is largely converted to heat in the glass
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b
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At the same time an astronaut on the moon sees a solar eclipse, observers on Earth see a) no eclipse at all b) a lunar eclipse c) a solar eclipse
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b
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Things seen by moonlight usually aren't colored because moonlight a) is too dim to activate the retina's cones b) photons dont have enough energy to activate the retina's cones c) doesn't have very many colors in it d) all of these e) none of these
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a
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What is the wavelength of an electromagnetic wave that has a frequency of 1 hertz? a) 1 m b) less than 1 m c) more than 1 m
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c
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The main difference between a radio wave and a sound wave is their different a) modes of travel b) energies c) amplitudes d) wavelengths e) frequencies
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a
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If a light signal and a radio signal were emitted simultaneously from Alpha Centauri, the first to reach Earth would be the a) light signal b) radio signal c) both would reach earth at the same time
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c
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Which of the following cannot travel in a vacuum? a) a light wave b) a radio wave c) a sound wave d) all can travel in a vacuum e) none can travel in a vacuum
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c
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Red-hot and blue-hot stars appear white to the eye because a) they are too dim to fire the rods b) the eye has difficulty seeing color at night c) they are too dim to fire the cones d) eye receptivity peaks in the yellow-green part of the spectrum e) they are overwhelmed by the blackness of the nighttime sky
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c
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The Earth's atmosphere is transparent to most waves in the a) ultraviolet part of the spectrum b) infrared part of the spectrum c) entire electromagnetic spectrum d) visible part of the spectrum
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d
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sunburns are produced by a) visible light b) ultraviolet light c) infrared light d) all of these e) none of these
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b
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Consider light energy that is momentarily absorbed in glass and then re-emitted. Compared to the absorbed light, the frequency of the re-emitted light is a) the same b) considerably less c) considerably more d) slightly less e) slightly more
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a
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Which of the following is fundamentally different from the others? a) light waves b) x-rays c) gamma rays d) radio waves e) sound waves
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e
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The natural frequency of the atoms in glass is in the a) ultraviolet part of the spectrum b) visible part of the spectrum c) infrared part of the spectrum
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a
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The main difference between a radio wave and a light wave is its a) wavelength b) speed c) frequency d) all of these e) two of these
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e
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Compared to radio waves, the velocity of visible light waves in a vacuum is a) the same b) more c) less
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a
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The source of all electromagnetic waves is a) accelerating electric charges b) vibrating atoms c) changes in atomic energy levels d) crystalline fluctuations e) none of these
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a
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Short wavelengths of visible light interact more frequently with the atoms in glass than do longer wavelengths. Does this interaction time tend to speed up or to slow down the average speed of short-wavelength light in glass? a) speed up b) slow down
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b
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A helium-neon laser emits light of wavelength 633 nanometers (nm). Light from an argon laser has a wavelength of 515 nm. Which laser emits the higher-frequency light? a) a helium neon laser b) an argon laser
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b
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Which of the following changes when light is refracted? a) reflective index b) speed c) frequency d) color
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b
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The light in raindrops making up a rainbow has undergone refraction and internal _______. a) reflection b) absorption c) scattering d) dispension
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a
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Total internal reflection occurs when the speed of light in a material is _______. a) less than the speed outside the material b) the same as the speed outside the material c) more than the speed outside the material d) either less than or greater than the speed outside the material
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a
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A magnifying glass widens the angle through which _______. a) refraction is amplified b) lower frequencies of the light are amplified c) higher frequencies of light are amplified d) an object is viewed
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d
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If the speed of light in a medium is , the medium's index of refraction is a) 0.67 b) 1.5 c) 0.50 d) 2.0 e) 1.0
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b
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Ninety percent of light incident on a certain piece of glass passes through it. How much light passes through two pieces of this glass? a) 90 % b) 85 % c) 81 % d) 89 % e) 80 %
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c
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When a pulse of white light is incident on a piece of glass, strictly speaking, the first color to emerge is a) orange b) red c) violet d) green e) they all emerge at the same time
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b
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The moon's redness during a lunar eclipse results from a) an optical illusion b)refraction by the Earth's atmosphere of Earth's sunrises and sunsets. c) only lower frequencies being reflected from the moon d) infrared radiation that is normally blocked e) none of these
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b
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When light is refracted, there is a change in its a) wavelength b) frequency c) both of these d) neither of these
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a
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Objects infinitely far away are focused by a converging lens a) at the focal point b) beyond the focal point c) in front of the focal point
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a
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When white light goes from air into water, the color that refracts the most is a) violet b) green c) orange d) red e) all refract the same amount
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a
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Rainbows exist because light is a) refracted b) reflected c) both of these d) neither of these
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c
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If a fish looks upward at 45 degrees with respect to the water's surface, it will see a) the bottom of the pond b) the sky and possibly some hills c) only the waters surface d) another fish in the pond e) none of these
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b
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When the pinhole in a pinhole camera is made larger, the image is a) clearer b) brighter c) both d) neither
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b
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The image of the "infinitely-far-away" sun produced by a converging lens appears a) at the focal point b) between the lens and the focal point c) beyond the focal point
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a
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The critical angle is least in which of the following? a) vacuum b) glass c) diamond d) water
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c
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The critical angle for a transparent material is the angle at and beyond which all light within the material is a) diffused b) refracted c) reflected d) dispensed e) absorbed
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c
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Rainbows are not usually seen as complete circles because a) the ground is usually in the way b) they are actually elliptical c) they have no bottom part d) rainbows are actually arched shaped e) raindrops are not perfectly round
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a
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Different colors are dispersed by a prism because different colors in the prism have different a) frequencies b) directions c) energies d) speeds e) none of these
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d
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The average speed of light is greatest in a) orange glass b) blue glass c) red glass d) green glass e) is the same in all of these
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c
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As a light ray in air at 15 degrees from the normal enters water, it a) sometimes bends toward the normal b) does not bend c) always bends toward the normal d) always bends away from the normal
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c
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Two plane mirrors are at right angles to each other. A coin placed near the mirrors has at most a) 3 images b) 2 images c) 4 images d) more than 4 images
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a
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The inversion of your image in a plane mirror is actually an inversion of a) up down b) front back c) left right d) all of these
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b
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A diver shines light up to the surface of a smooth pond at a 10-degree angle to the normal. Some light passes into the air above, and the part that reflects back into the water makes an angle to the normal of a) less than 10 degrees b) 10 degrees c) more than 10 degrees
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b
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To see his full height, a boy that is 1 meter tall needs a mirror that is at least a) 0.75 m tall b) 1 m tall c) 0.50 m tall d) 0.33 m tall e) depends on how far the mirror is from the boy
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c
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If you walk towards a mirror at a certain speed, the relative speed between you and your image is a) your speed b) twice your speed c) half your speed d) none of these
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b
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When light reflects from a surface, there is a change in its a) speed b) wavelength c) frequency d) all of these e) none of these
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e
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The amount of light reflected from the front surface of a common windowpane is about a) 92 percent b) 40 percent c) 8 percent d) 96 percent e) 4 percent
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e
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Object and image for a plane mirror lie a) along the same plane b) at right angles to each other c) equal distances from the mirror d) all of these e) none of these
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c
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When your eye is submerged in water, is the bending of light rays from water to your eyes more, less, or the same as in air? a) less b) more c) the same
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a
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Light is emitted when a) electromagnetic waves emanate from matter b) electron clouds of atoms are forced into oscillation c) high frequency sound waves strike matter d) atomic nuclei are made to vibrate
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b
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Light refracts when traveling from air into glass because light a) has greater intensity in glass than in air b) travels slower in glass than in air c) has greater frequency in air than in glass d) has greater frequency in glass than in air e) has greater intensity in air than in glass
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b
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Refraction results from differences in light's a) frequency b) speed c) incident angles d) all of these e) none of these
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b
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Chromatic aberration is absent in a) front surface plane mirrors b) converging lenses c) diverging lenses
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a
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A beam of light travels fastest in a) glass b) water c) plastic d) air e) is the same in each of these
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d
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A person standing waist-deep in a swimming pool appears to have short legs because of light a) interference b) refraction c) diffraction d) reflection e) absorption
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b
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A mirage is the result of atmospheric _______. a) refraction b) air inversions c) bending d) reflection
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a
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The blackness of the type on a page is due to _______. a) scattering b) reflection c) interference d) absorption
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d
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Light travels a path from one location to another in the least _______. a) energetic path b) time c) distance d) dense material
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b
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Specular reflection is common in the light reflected from _______. a) a common road b) a mirror c) a rough surface d) this page
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b
