PHYS 1060 Spring 2011 - Final

A reclusive fashion designer takes the dog for a walk on a treadmill. The treadmill's surface moves toward the left as the dog and designer walk toward the right, so that the two of them remain exactly in place. The dog is pulling its leash toward the right and the designer is pulling that leash toward the left. Which of the following is true?

(A) Neither the designer nor the dog is doing work on the leash. [75.2% picked]

(B) The designer is doing work on the leash and the leash is doing work on the dog. [3.6% picked]

(D) The dog is doing work on the leash and the leash is doing work on the designer. [6.4% picked]

Answer: (A) Neither the designer nor the dog is doing work on the leash. [75.2% picked]

(A) it contains martensite crystals, which are much harder than ordinary ferrite crystals. [8.4% picked]

(B) its surface layer is compressed by the tense core of the glass. [77.2% picked]

(D) its surface layer is almost pure quartz glass, which is stronger than soda-lime-silica glass. [6.8% picked]

Answer: (B) its surface layer is compressed by the tense core of the glass. [77.2% picked]

The electrons in a large atom aren't all in the lowest energy orbital (the orbital closest to the atom's nucleus). That's because

(A) two identical electrons can never be in the same quantum wave. [49.2% picked]

(B) the electrons are repelled by the nucleus and move away from it. [7.6% picked]

(D) the nuclear force prevents electrons from approaching the atom's nucleus, so they distribute themselves uniformly among the atom's outer orbitals. [36.0% picked]

Answer: (A) two identical electrons can never be in the same quantum wave. [49.2% picked]

There are two wires connecting your laptop's brick-shaped power adapter to the computer itself. Each wire has a voltage and each wire carries a current. Which of the following correctly describes the voltages and currents in those wires?

(A) Current flows from the adapter to the computer through the wire with the lower voltage. Current flows from the computer to the adapter through the wire with the higher voltage. [15.6% picked]

(B) The voltages of the two wires alternate, so the current flow in each wire reverses with each alternation of that voltage. [25.2% picked]

(C) Current flows from the adapter to the computer through the wire with the higher voltage. Current flows from the computer to the adapter through the wire with the lower voltage. [58.8% picked]

(D) Each wire has a positive voltage, so each wire carries current from the adapter to the computer. [0.4% picked]

Answer: (C) Current flows from the adapter to the computer through the wire with the higher voltage. Current flows from the computer to the adapter through the wire with the lower voltage. [58.8% picked]

The f-number of a camera lens is the ratio of its focal length to its diameter (f-number = focal length / diameter). As the f-number of a lens decreases,

(A) the brightness of the real image increases and the depth of focus decreases. [52.4% picked]

(B) the depth of focus increases and the brightness of the real image decreases. [23.2% picked]

(D) the depth of focus increases and the size of the real image decreases. [13.6% picked]

Answer: (A) the brightness of the real image increases and the depth of focus decreases. [52.4% picked]

When an electron with a great deal of kinetic energy passes very near the massive nucleus of a large atom, the electron's direction suddenly changes. The electron emits an X-ray because

(A) the passing electron causes a current to flow in the nucleus, releasing the electromagnetic wave. [12.4% picked]

(B) sliding friction causes its temperature to increase and it begins to glow white hot. It becomes so hot that it emits X-rays. [0.4% picked]

(C) an accelerating electric charge emits an electromagnetic wave and this very abrupt acceleration produces a very high frequency wave. [78.0% picked]

(D) a moving electric charge emits a visible electromagnetic wave but this wave becomes an X-ray when it is emitted near an atomic nucleus. [6.4% picked]

Answer: (C) an accelerating electric charge emits an electromagnetic wave and this very abrupt acceleration produces a very high frequency wave. [78.0% picked]

When molten copper is allowed to cool in the shape of a knife, the resulting blade is extremely soft. Hammering that blade repeatedly hardens the copper because

(A) the atoms in beaten copper bond more tightly to one another. [12.4% picked]

(B) beaten copper is no longer crystalline. [2.0% picked]

(D) the beaten copper crystals are much more resistant to slip (sliding of their atomic layers). [82.0% picked]

Answer: (D) the beaten copper crystals are much more resistant to slip (sliding of their atomic layers). [82.0% picked]

Compared to an ordinary alkaline AA battery, an ordinary alkaline D battery provides

(A) a larger voltage rise and can supply more total electrical energy. [2.4% picked]

(B) the same voltage rise and can supply the same total electrical energy. [0.4% picked]

(D) the same voltage rise but can supply more total electrical energy. [93.2% picked]

Answer: (D) the same voltage rise but can supply more total electrical energy. [93.2% picked]

The light wave traveling through an optical fiber remains inside that fiber's core because it experiences total internal reflection each time it encounters the core's outer surface. How does the speed at which light travels in the core compare to the speed at which light travels in the cladding surrounding that core?

(A) Light travels more slowly in the core than in the cladding. [51.2% picked]

(B) Trick question! The cladding is mirrored, so light can't travel in it at all. [9.2% picked]

(D) Light travels faster in the core than in the cladding. [35.2% picked]

Answer: (A) Light travels more slowly in the core than in the cladding. [51.2% picked]

A motor/generator is a single device that can act as a motor or a generator. Suppose that you are twisting the rotor of a motor/generator with your hand while that rotor is rotating. The device acts as a motor when you twist the rotor

(A) counterclockwise. [0.8% picked]

(B) in the direction of its rotation. [16.8% picked]

(D) clockwise. [1.2% picked]

(A) one divided by the voltage difference between the two ends of the wire. [20.0% picked]

(B) the net charge of that wire. [11.6% picked]

(D) one divided by the net charge of that wire. [6.0% picked]

Answer: (C) the voltage difference between the two ends of the wire. [60.8% picked]

If you exert a force of 100 N on a heavy file cabinet as it accelerates forward, the file cabinet will push back on you with

(A) a force of more than 100 N. [0.0% picked]

(B) zero force until it comes to a stop. [0.8% picked]

(D) a force of 100 N. [91.6% picked]

One way for a jeweler to check if a gemstone is genuine is to immerse that gemstone in a clear, colorless liquid that has the same refractive index as the real gemstone. In other words, light travels at the same speed in the liquid as in the real gemstone. When the real gemstone is in that liquid,

(A) the gemstone's surfaces become invisible and only the color of the gemstone (if any) can be seen. [37.6% picked]

(B) the gemstone exhibits total internal reflection from all of the surfaces on its far side (the side opposite the jeweler) and the back of the gemstone appears to be mirrored. [4.4% picked]

(D) the gemstone becomes opaque and no light is visible through it. [1.2% picked]

Answer: (A) the gemstone's surfaces become invisible and only the color of the gemstone (if any) can be seen. [37.6% picked]

(A) 5 are metal and 1 is metal mesh. [82.8% picked]

(B) 5 are plastic and 1 is metal mesh. [8.4% picked]

(D) 5 are metal and 1 is plastic mesh. [6.0% picked]

(A) water molecules have a large magnetic dipole (a north pole and a south pole). [33.2% picked]

(B) water molecules have a large net charge. [7.2% picked]

(D) water molecules have a large electric dipole (a positive end and a negative end). [49.6% picked]

Answer: (D) water molecules have a large electric dipole (a positive end and a negative end). [49.6% picked]

You have two bowling balls, one of which weighs twice as much as the other. The balls roll off a horizontal table at the same time and at the same velocity. In this situation, both balls hit the floor

(A) at approximately the same time and at the same distance from the table. [86.4% picked]

(B) at approximately the same time, but the heavier ball hits considerably farther from the table than the lighter ball. [9.6% picked]

(C) at approximately the same distance from the table, but the heavier ball hits the floor well before the lighter ball. [3.2% picked]

(D) at approximately the same distance from the table, but the lighter ball hits the floor well before the heavier ball. [0.8% picked]

Answer: (A) at approximately the same time and at the same distance from the table. [86.4% picked]

Your hairdryer was designed to operate on 120 volt alternating current, but you are traveling in Europe and your friend connects it to 230 volt alternating current. The hairdryer quickly burns out because

(A) the correct amount of current flows through the hairdryer's heating element, but that current produces too many volts in the heating element and burns it up. [13.2% picked]

(B) the correct amount of current flows through the hairdryer's heating element, but that current alternates too rapidly and overheats the heating element. [8.4% picked]

(C) the temperature of 230 volt alternating current is much higher than the hairdryer was designed to handle and it burns up the hairdryer. [5.6% picked]

(D) the voltage gradient in the hairdryer's heating element is too large and too much current flows through the heating element. [72.8% picked]

Answer: (D) the voltage gradient in the hairdryer's heating element is too large and too much current flows through the heating element. [72.8% picked]

The transformer in a power adapter has 120 turns in its primary coil and 6 turns in its secondary coil. With 120 volt AC power connected to the primary coil and a current of 1 ampere flowing through that primary coil, the transformer's secondary coil is supplying

(A) 20 volt AC power and a current of 6 amperes is flowing through that secondary coil. [24.0% picked]

(B) 20 volt AC power and a current of 20 amperes is flowing through that secondary coil. [0.4% picked]

(D) 6 volt AC power and a current of 20 ampere is flowing through that secondary coil. [72.4% picked]

Answer: (D) 6 volt AC power and a current of 20 ampere is flowing through that secondary coil. [72.4% picked]

(A) it has such a poor thermal conductivity that only its outer layer will melt during recycling. [19.2% picked]

(B) it is essentially a single giant molecule and cannot melt. [73.6% picked]

(D) it is too dense to melt. [7.2% picked]

Answer: (B) it is essentially a single giant molecule and cannot melt. [73.6% picked]

Atoms are often drawn as having planet-like electrons traveling in circular orbits around a sun-like nucleus. This characterization is naive primarily because the electrons in an atom

(A) exist as quantum standing waves surrounding the nucleus. [78.0% picked]

(B) can also travel in elliptical and parabolic orbits. [4.0% picked]

(D) are much, much smaller than the nucleus. [5.6% picked]

Answer: (A) exist as quantum standing waves surrounding the nucleus. [78.0% picked]

Two similar fluorescent lamp tubes produce different variations on white light. One tube produces the "warm white" of an incandescent lamp while the other tube produces the "cool white" of sunlight. Those two tubes differ primarily in

(A) the phosphor coatings they have on the inside of their glass. [64.0% picked]

(B) the mixtures of gases they contain. [29.2% picked]

(D) the colors of the white paints they have on the insides of the glass. [5.6% picked]

Answer: (A) the phosphor coatings they have on the inside of their glass. [64.0% picked]

You are boating on a vast lake and listening to an AM radio station. You can see the station's vertical transmitting antenna on the shore, directly to your south. As that station's radio wave passes by you, its electric field points

(A) vertically up and down and its magnetic field points horizontally north and south [20.4% picked]

(B) horizontally east and west and its magnetic field points horizontally north and south. [2.0% picked]

(D) vertically up and down and its magnetic field points horizontally east and west. [75.6% picked]

Answer: (D) vertically up and down and its magnetic field points horizontally east and west. [75.6% picked]

You have a charged ball, a neutral metal plate, and a neutral glass plate. If you place a charged balloon near each of these three objects, which of them will cause the balloon to accelerate? Neglect air effects and gravity.

(A) Only the charged ball will cause the balloon to accelerate. [46.8% picked]

(B) All three objects will cause the balloon to accelerate. [42.0% picked]

(D) Only the neutral metal plate will cause the balloon to accelerate. [8.0% picked]

Answer: (B) All three objects will cause the balloon to accelerate. [42.0% picked]

Nearly all of the nuclear reactors in the United States are of a type known as "thermal fission reactors." What does the word "thermal" refer to?

(A) The reactor's core is enveloped in a cooling jacket to keep its temperature near room temperature. [2.4% picked]

(B) The fast-moving fission neutrons are slowed in a moderator so that they move at thermal (slow) speeds. [41.6% picked]

(C) The reactor's chain reaction produces heat, rather than radiation. That heat is then used to generate electricity. [30.4% picked]

(D) The fission events in the reactor core occur at high temperatures, where they are most efficient. [24.8% picked]

Answer: (B) The fast-moving fission neutrons are slowed in a moderator so that they move at thermal (slow) speeds. [41.6% picked]

A radio wave is passing you, heading toward your right. At this moment, the wave's electric field has reached its peak upward strength directly in front of your nose (you are looking at a crest of the wave). Over the next period of time, the wave's electric field changes to point downward and then returns to its peak upward value again. During that period of time, the original crest that was in front of your nose has moved

(A) 1/2 a wavelength to the right of your nose. [5.6% picked]

(B) 2 wavelengths to the right of your nose. [6.0% picked]

(D) a distance equal to the speed of light to the right of your nose. [5.6% picked]

If you heat pure iron until it is yellow hot and then quench it rapidly to room temperature, it will

(A) not harden because carbon is need to form martensite crystals. [10.8% picked]

(B) harden because when pure iron is quenched it becomes steel. [6.8% picked]

(C) not harden because the quenched iron will remain in its high-temperature crystalline form (austenite). [20.4% picked]

(D) harden because the quenched iron forms martensite crystals. [60.8% picked]

Answer: (A) not harden because carbon is need to form martensite crystals. [10.8% picked]

On a clear day, the sky appears blue because some visible light from the sun experiences Rayleigh scattering. But sunlight also contains infrared light (longer wavelength than red) and ultraviolet light (shorter wavelength than violet). Along with the blue light, does the sky also scatter much infrared and/or ultraviolet light?

(A) The sky scatters a large amount of ultraviolet light, but very little infrared light. [91.2% picked]

(B) The sky scatters very little infrared light or ultraviolet light. [2.4% picked]

(D) The sky scatters a large amount of infrared light, but very little ultraviolet light. [3.2% picked]

Answer: (A) The sky scatters a large amount of ultraviolet light, but very little infrared light. [91.2% picked]

If you hit a pure iron sheet with a hardened steel hammer, the iron sheet will dent but the hammer will not dent. Both objects are almost pure iron, so why does only the iron sheet dent?

(A) The iron atoms in the hammer are crystallized and therefore cannot move, while the iron atoms in the iron sheet are not crystallized and can easily shift from one place to another. [2.4% picked]

(B) The small crystals of iron atoms in the iron sheet can move easily past one another, while the large crystals of iron atoms in the hardened hammer resist that motion. [5.2% picked]

(C) The large crystals of iron atoms in the iron sheet can move easily past one another, while the small crystals of iron atoms in the hardened hammer resist that motion. [4.0% picked]

(D) The uniform layers of iron atoms in the iron sheet can slip across one another, while the distorted layers of iron atoms in the hardened hammer resist slipping. [88.4% picked]

Answer: (D) The uniform layers of iron atoms in the iron sheet can slip across one another, while the distorted layers of iron atoms in the hardened hammer resist slipping. [88.4% picked]

How does the molecular structure of solid glass compare to the structure of liquid glass?

(A) Both have crystalline structures, but liquid glass's crystals are so tiny that they can move relative to one another and the glass can change its shape. [14.4% picked]

(B) Both have similar crystalline structures, but only the liquid glass can undergo slip in order to flow in response to stress. [31.2% picked]

(C) Both have similar disordered structures, but only the liquid glass can flow in response to stress or strain. [27.2% picked]

(D) Solid glass has an orderly crystalline structure whereas liquid glass has a disordered structure. [26.8% picked]

Answer: (C) Both have similar disordered structures, but only the liquid glass can flow in response to stress or strain. [27.2% picked]

A microwave oven moves the food around on a carousel to obtain relatively even heating. Motionless food would heat unevenly because

(A) the water molecules cannot exchange heat via conduction while the food is stationary. [5.6% picked]

(B) of constructive and destructive interference between the many microwave reflections. [90.4% picked]

(D) the water molecules cannot undergo convection unless the food is in motion. [2.4% picked]

Answer: (B) of constructive and destructive interference between the many microwave reflections. [90.4% picked]

Separating uranium-235 from uranium-238 is extremely difficult because atoms of these two isotopes have the same number of

(A) neutrons and therefore the same chemistry. [19.2% picked]

(B) protons plus neutrons and therefore the same mass. [16.0% picked]

(D) electrons and therefore the same chemistry. [59.6% picked]

When you heat iron until it is almost yellow hot, it abruptly loses its ability to attract a magnet. The iron loses its magnetism because

(A) its electrons lose their magnetic dipoles and can no longer give the iron any magnetic character. [16.0% picked]

(B) its crystal structure changes and its high-temperature crystal form (austenite) is non-magnetic. [70.0% picked]

(D) electric current stops flowing in the iron and the iron stops being an electromagnet. [7.2% picked]

Answer: (B) its crystal structure changes and its high-temperature crystal form (austenite) is non-magnetic. [70.0% picked]

You have two identical electric space heaters, both of which are plugged into the same electrical outlet of your home. It's a cold winter day and you turn on one of the heaters. A current of 8 amperes flows through the wires of your home (to provide power to the heater) and wastes 1 watt in those wires. When you turn on the second heater, a current of

(A) 8 amperes flows through the wires of your home and wastes 2 watts in those wires. [4.8% picked]

(B) 16 amperes flows through the wires of your home and wastes 2 watts in those wires. [13.2% picked]

(D) 32 amperes flows through the wires of your home and wastes 2 watts in those wires. [1.6% picked]

Answer: (C) 16 amperes flows through the wires of your home and wastes 4 watts in those wires. [80.4% picked]

As a drop of clear, colorless oil spreads out on the top surface of a puddle, you can see colored rings in the light reflected from the thin layer of oil. What is causing those colored rings?

(A) Light is refracting at the surface of the oil and, because violet light travels faster in the oil than red light, the light separates into the colors of the rainbow. [16.0% picked]

(B) The clear oil is separating into its primary colors of pigment as it spreads outward on the water. [0.0% picked]

(D) The clear oil is separating into its primary colors of light as it spreads outward on the water. [2.0% picked]

Answer: (C) The reflections from the oil layer's top and bottom surfaces are interfering with one another. [82.0% picked]

A laser emits coherent light--a single giant electromagnetic wave. The laser produces that coherent light by

(A) controlling the wavelengths of the photons emitted by a collection of excited atoms so that they emit their photons spontaneously with exactly the same wavelength. [10.8% picked]

(B) duplicating a single initial photon many times to obtain a vast number of identical photons. [74.0% picked]

(D) controlling the direction of the photons emitted by a collection of excited atoms so that they emit their photons spontaneously in exactly the same direction. [4.4% picked]

Answer: (B) duplicating a single initial photon many times to obtain a vast number of identical photons. [74.0% picked]

Unlike pure semiconductor, n-type semiconductor has some filled conduction levels and p-type semiconductor has some empty valence levels. Suppose you have two electrically neutral disks, one of n-type semiconductor and one of p-type semiconductor. When you touch the two disks, electrons migrate from the

(A) n-type semiconductor to the p-type semiconductor and the resulting electric field points from the n-type semiconductor toward the p-type semiconductor. [66.4% picked]

(B) p-type semiconductor to the n-type semiconductor and the resulting electric field points from the n-type semiconductor toward the p-type semiconductor. [2.4% picked]

(C) p-type semiconductor to the n-type semiconductor and the resulting electric field points from the p-type semiconductor toward the n-type semiconductor. [3.6% picked]

(D) n-type semiconductor to the p-type semiconductor and the resulting electric field points from the p-type semiconductor toward the n-type semiconductor. [26.4% picked]

Answer: (A) n-type semiconductor to the p-type semiconductor and the resulting electric field points from the n-type semiconductor toward the p-type semiconductor. [66.4% picked]

(A) The cylindrical polyethylene molecules are sticky and they cling to one another with stretchy chemical forces. [1.6% picked]

(B) The chainlike polyethylene molecules are tangled and, while those chains can move relative to one another, they cannot untangle. [94.8% picked]

(C) The spherical polyethylene molecules are oppositely charged and attract one another strongly enough to give the bag its stretchy strength. [0.8% picked]

(D) The rodlike polyethylene molecules are linked together by springs that can stretch without breaking. [2.4% picked]

Answer: (B) The chainlike polyethylene molecules are tangled and, while those chains can move relative to one another, they cannot untangle. [94.8% picked]

Medical radiation therapy usually involves gamma rays produced by the radioactive decay of cobalt-60 or by an electron accelerator and a tungsten target. Those gamma rays kill cancerous tissue because

(A) each gamma ray is so massive that it knocks atoms out of place in the cells and disrupts their function. [9.2% picked]

(B) each gamma ray photon carries enough energy to shatter many molecules. [49.6% picked]

(C) each gamma ray is so intense that it heats the tissue until proteins are denatured (deformed into dysfunctional forms). [19.6% picked]

(D) the frequency of a gamma ray is so high that it vibrates electrons until those electrons are destroyed. [19.6% picked]

Answer: (B) each gamma ray photon carries enough energy to shatter many molecules. [49.6% picked]

To sustain a nuclear chain reaction, an assembly of fissionable material must ensure that, on average,

(A) each neutron causes the release of at least one neutron. [60.0% picked]

(B) each proton causes the release of at least one proton. [1.2% picked]

(D) each fission produces at least two radioactive fission fragments. [22.0% picked]

Answer: (A) each neutron causes the release of at least one neutron. [60.0% picked]

A juggler throws a chainsaw into the air. During the time that the chainsaw is not touching the ground and neglecting any effects due to the air, the one aspect of the chainsaw's motion that is constant is the chainsaw's

(A) angular velocity. [9.6% picked]

(B) angular momentum. [82.4% picked]

(D) momentum. [6.0% picked]

A dolphin leaps straight up out of the water, rises high above the water, and then drops back into the water. When the dolphin left the water, its momentum was in the upward direction. When it returned to the water, its momentum was in the downward direction. While it was not touching the water, what happened to the dolphin's initial upward momentum?

(A) Its upward momentum was converted into thermal energy. [0.4% picked]

(B) Its upward momentum was converted into gravitational potential energy. [8.8% picked]

(D) Its upward momentum was transferred to the earth. [88.0% picked]

A CD player was developed in the 1980s and uses an infrared laser. A blu-ray player was developed in the past decade and uses a blue laser. A blu-ray disc can hold far more information than a CD because

(A) The blue laser light is brighter than the infrared laser light. [0.8% picked]

(B) The blue laser light has a shorter wavelength than the infrared laser light. [84.4% picked]

(D) Blue light is much easier to detect than infrared light and this increased sensitivity allows the blu-ray disc to pack information more tightly. [14.4% picked]

Answer: (B) The blue laser light has a shorter wavelength than the infrared laser light. [84.4% picked]

The positive terminal and negative terminal of a 9 volt battery are about 1/4 inch apart. In keeping with its name, the battery's positive terminal has a voltage that is 9 volts greater than the voltage of its negative terminal. Midway between those two terminals, the electric field

(A) is zero. [3.2% picked]

(B) points away from the positive terminal and toward the negative terminal. [74.0% picked]

(D) is 4.5 volts. [7.2% picked]

Answer: (B) points away from the positive terminal and toward the negative terminal. [74.0% picked]

Both CT scans (Computed Tomography) and MRI images (Magnetic Resonance Imaging) expose the patient to radiation. Which of these imaging techniques involves exposure to ionizing (and therefore hazardous) radiation?

(A) Only MRI imaging. [20.4% picked]

(B) Both CT scanning and MRI imaging. [18.0% picked]

(D) Only CT scanning. [30.0% picked]

(A) have relatively large numbers of protons and neutrons. [20.4% picked]

(B) have relatively large numbers of electrons. [42.8% picked]

(D) have relatively large masses. [28.4% picked]

When you hold a disk-shaped converging lens in bright sunlight, a dazzlingly bright, circular spot forms on a sheet of paper. The paper begins to smoke and burn. The spot of light on the paper is circular because

(A) it is a real image of the circular sun. [92.4% picked]

(B) the lens is circular. [1.2% picked]

(C) the wave nature of light prevents it from converging to a true point in space and spreads the light into a circular patch that is brightest at its center. [4.8% picked]

(D) the wave nature of light prevents it from converging to a true point in space and spreads the light into a circular patch that has a uniform brightness. [1.6% picked]

(A) becomes equal to that of a microwave. [0.4% picked]

(B) becomes shorter. [94.8% picked]

(D) stays the same. [2.8% picked]

A large glass bowl is almost perfectly clear. If you crush that bowl into powder, it becomes white because

(A) light passing through it experiences total internal reflection. [4.4% picked]

(B) light passing through it travels at the same speed, regardless of wavelength. [2.4% picked]

(D) each surface in the crushed glass partially reflects light. [92.0% picked]

Answer: (D) each surface in the crushed glass partially reflects light. [92.0% picked]

The colors that you see when sunlight strikes a cut crystal wineglass or a cut diamond are a result of the fact that two light waves with

(A) different frequencies in air can have the same wavelength in a material. [0.4% picked]

(B) the same frequency can have different colors. [0.4% picked]

(D) different frequencies travel at different speeds in most materials. [74.4% picked]

Answer: (D) different frequencies travel at different speeds in most materials. [74.4% picked]

The MOSFET device that we discussed in class and in the book consists of a p-type semiconductor "channel" layer sandwiched between two n-type semiconductor layers (the "source" and the "drain"). By themselves, these three layers block the flow of current between the source and drain. But putting positive charge on the "gate" surface, located very near the channel layer, allows the MOSFET to conduct current by

(A) pushing positive charge out of the channel, where that positive charge had been blocking the flow of electric current. [11.6% picked]

(B) attracting electrons into the channel layer, so that it behaves like n-type semiconductor. [61.2% picked]

(C) bending the channel toward the gate surface and removing the kink that had been pinching off the flow of electric current. [2.4% picked]

(D) attracting electrons into the channel layer, so that it behaves like p-type semiconductor. [24.0% picked]

Answer: (B) attracting electrons into the channel layer, so that it behaves like n-type semiconductor. [61.2% picked]

You are pulling a toy wagon up a steep hill and the wagon is traveling in a straight line at a steady pace. The net force that the wagon is experiencing

(A) points straight up. [1.2% picked]

(B) points uphill. [0.8% picked]

(D) is zero. [94.4% picked]

You stand near the bottom of a flagpole and throw a stone straight upward. The stone leaves your hand at the bottom of the flagpole and rises for 2 seconds to the top of the flagpole, where it is momentarily motionless. After it has risen for only 1 second, where is the stone located? Neglect air effects.

(A) The stone is halfway up the flagpole. [1.2% picked]

(B) The stone is much closer to the bottom of the flagpole than it is to the top of the flagpole. [24.0% picked]

(D) The stone is a few inches above halfway up the flagpole. [2.8% picked]

Answer: (C) The stone is much closer to the top of the flagpole than it is to the bottom of the flagpole. [72.0% picked]

(A) toward the charge and becomes weaker with increasing distance from the charge. [13.6% picked]

(B) toward the charge and does not depend on the distance from the charge. [0.4% picked]

(D) away from the charge and becomes weaker with increasing distance from the charge. [85.2% picked]

Answer: (D) away from the charge and becomes weaker with increasing distance from the charge. [85.2% picked]

How should you alter a camera’s lens to make a distant object appears larger in the photographs?

(A) Decrease the diameter of the lens. [15.6% picked]

(B) Increase the curvature of the lens. [37.2% picked]

(D) Decrease the curvature of the lens. [27.2% picked]

Three factory workers are loading dozens of identical office chairs into a truck. These wheeled chairs are located on the ground behind the truck. The first person lifts chairs straight up into the truck. The second person rolls chairs slowly up a long, gradual ramp into the truck. The third person rolls chairs slowly up a short, steep ramp into the truck. Neglecting friction, which person does the most work on each chair while transferring it from the ground to the back of the truck?

(A) The three people do the same amount of work on each chair. [87.2% picked]

(B) The second person does the most work on each chair. [2.0% picked]

(D) The third person does the most work on each chair. [2.8% picked]

Answer: (A) The three people do the same amount of work on each chair. [87.2% picked]

When a high-pressure mercury streetlamp first turns on, that lamp emits a dim, purple light. Over the next 5 minutes or so, its light becomes brighter and whiter because, as the pressure of mercury in the lamp increases, the mercury atoms

(A) begin to pack into crystals that emit brighter and whiter light. [3.2% picked]

(B) collide more often and thereby emit a richer variety of wavelengths. [61.6% picked]

(D) begin to move faster and have more energy, so they are able to emit a richer variety of wavelengths. [26.4% picked]

Answer: (B) collide more often and thereby emit a richer variety of wavelengths. [61.6% picked]

(A) A positively charged banker bouncing directly up and down on a trampoline. [72.4% picked]

(B) A positively charged lawyer riding straight up in an elevator at constant speed. [7.6% picked]

(D) A negatively charged doctor swimming horizontally at constant velocity. [8.4% picked]

Answer: (A) A positively charged banker bouncing directly up and down on a trampoline. [72.4% picked]

(A) builds steadily in a magnetic field. [2.8% picked]

(B) builds steadily in an electric field. [6.0% picked]

(D) builds steadily in an electric field and a magnetic field, each of which contains half the total energy. [4.0% picked]

Answer: (C) shifts back and forth rhythmically between a magnetic field and an electric field. [85.6% picked]

A twist-tie is a long, thin, sharp metal wire wrapped in paper. If you place a twist-tie in a microwave oven and turn the oven on, what will happen to the twist-tie?

(A) An electric current will flow through it, heating it up, and electric charge will also spray out of its sharp ends. [72.8% picked]

(B) The twist tie will remain cool, but electric charge will spray out of its sharp ends. [18.4% picked]

(D) The twist tie will not be affected by the microwaves because it contains no water. [1.2% picked]

Answer: (A) An electric current will flow through it, heating it up, and electric charge will also spray out of its sharp ends. [72.8% picked]

You use a converging lens to project the image of a flower on the wall of your dorm room. What should that lens do to form a sharp image of the flower on the wall?

(A) The lens should bend the light rays from a single point on the flower so that they converge to a single point on the wall. [32.8% picked]

(B) The lens should converge all of the light rays from the flower so that they meet at a point half-way from the lens to the wall. Those rays will continue on to form a sharp image on the wall. [27.6% picked]

(C) The lens should bend the light rays from a single point on the flower so that they converge to a flower-shaped spot on the wall. [11.2% picked]

(D) The lens should bend the light rays from the entire flower so that they converge to a single point on the wall. [26.8% picked]

Answer: (A) The lens should bend the light rays from a single point on the flower so that they converge to a single point on the wall. [32.8% picked]