PHYS 1060 Midterm Exam 2, Spring 2010
Problem 1:
When a light wave is midway between a distant star and your eye, that wave consists of
(A) a magnetic field and either an electric field or an electric charge.
(B) an electric field and either a magnetic field or a magnetic pole.
(C) either an electric field or an electric charge, and either a magnetic field or a magnetic pole.
(D) an electric field and a magnetic field, but no electric charges or magnetic poles.
Problem 2:
You have just pulled your clothes from the dryer and find that a sock is clinging to your jeans with static electricity. You hold the jeans in one hand and the sock in the other and pull the two apart. As jeans and sock move apart, the forces between them become weaker because the
(A) electric current passing through each garment diminishes as they move apart.
(B) forces between electric charges become weaker with increasing distance.
(C) electric charge on each garment increases as they move apart.
(D) electric charge on each garment diminishes as they move apart.
Problem 3:
A microwave oven reheats your coffee by exposing that coffee to an intense microwave, an electromagnetic wave with a wavelength of about 12 cm. The coffee becomes hotter because
(A) the microwave is much hotter than the coffee and heat flows naturally from the hotter microwave to the cold coffee.
(B) the microwave's alternating electric field exerts torques on the polar water molecules in the coffee and those molecules rotate and rub against one another.
(C) the microwave's alternating electric field exerts forces on the charged water molecules in the coffee and those molecules move and collide with one another.
(D) the microwave undergoes Rayleigh scattering as it encounters the coffee and it vibrates the coffee molecules so that they become hotter.
Problem 4:
Compared to an ordinary AA battery, an ordinary D battery
(A) has the same voltage and can supply the same total electrical energy.
(B) has a higher voltage but can supply the same total electrical energy.
(C) has a higher voltage and can supply more total electrical energy.
(D) has the same voltage but can supply more total electrical energy.
Problem 5:
If the speed of light in water did not depend on the wavelength of that light, a rainbow would
(A) appear reversed in color, with red on the inside and violet on the outside.
(B) not appear at all.
(C) appear white.
(D) still appear red on the outside and violet on the inside.
Problem 6:
When the MOSFET device that we discussed in class and in the book has zero charge on its gate surface, its middle portion (the "channel") cannot conduct current. Putting positive charge on the gate surface can allow the MOSFET to conduct current by
(A) attracting electrons into the channel, where they fill some of the conduction levels.
(B) attracting electrons into the channel, so that the valence levels are then completely filled and the conduction levels are completely empty.
(C) bending the channel toward the gate surface and removing the kink that had been pinching off the flow of electric current.
(D) pushing positive charge out of the channel, where that positive charge had been blocking the flow of electric current.
Problem 7:
The sky is blue rather than pink at midday because
(A) tiny particles in the air are more efficient at Rayleigh scattering violet light waves than they are at scattering red light waves.
(B) tiny particles in the air absorb red light more efficiently than they absorb violet light.
(C) air molecules are slightly blue in color and they impart that color to the sunlight passing through them.
(D) sunlight that reflects from the blue oceans, seas, and lakes colors the sky blue.
Problem 8:
The transformer in a power adapter has 120 turns in its primary coil and 10 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) 12 volt AC power and a current of 10 ampere is flowing through that secondary coil.
(B) 10 volt AC power and a current of 10 amperes is flowing through that secondary coil.
(C) 10 volt AC power and a current of 12 amperes is flowing through that secondary coil.
(D) 12 volt AC power and a current of 12 amperes is flowing through that secondary coil.
Problem 9:
The electric motor in a toy car has a permanent magnet rotor and stationary electromagnets. When the motor is propelling the car, the poles of its electromagnets
(A) attract the rotor's poles as they approach and repel the rotor's poles as they separate.
(B) repel the rotor's poles as they approach and repel the rotor's poles as they separate.
(C) attract the rotor's poles as they approach and attract the rotor's poles as they separate.
(D) repel the rotor's poles as they approach and attract the rotor's poles as they separate.
Problem 10:
An acorn falls 20 meters from the high branch of an oak tree to the ground. This fall takes about 2 seconds. After it has fallen for only 1 second, the acorn is still falling and is located
(A) considerably more than 10 meters above the ground.
(B) 10 meters above the ground.
(C) just a little less than 10 meters above the ground.
(D) considerably less than 10 meters above the ground.
Problem 11:
When a beam of white sunlight passes through the crystal chandelier hanging over the ballroom of your new Hollywood mansion, it produce spots of light all over the room. Some of those spots look like tiny rainbows. The key physical effect that allows the chandelier's perfectly transparent crystals to form those colored rainbow spots is
(A) that different crystals emit different colors of light.
(B) that different wavelengths of light travel at slightly different speeds in the crystals.
(C) that all wavelengths of light travel at exactly the same speed in the crystals.
(D) that different crystals absorb different colors of light.
Problem 12:
A speedboat is pulling a water-skier with a rope and the skier is traveling forward in a straight line path at a constant speed. The net force experienced by the skier
(A) is zero.
(B) points in the forward direction.
(C) points in the upward direction.
(D) points in the backward direction.
Problem 13:
The voltage at the start of an ordinary wire is 10 volts and a current of 5 amperes enters that wire. The voltage at the end of the wire is
(A) less than 10 volts and a current of 5 amperes exits the wire.
(B) more than 10 volts and a current of 5 amperes exits the wire.
(C) more than 10 volts and a current of less than 5 amperes exits the wire.
(D) 10 volts and a current of 5 amperes exits the wire.
Problem 14:
A one-battery flashlight is turned on and is producing light. The current flowing through its lightbulb
(A) enters the lightbulb at higher voltage and exits at lower voltage. The current flowing through its battery enters the battery at lower voltage and exits at higher voltage.
(B) enters the lightbulb at lower voltage and exits at higher voltage. The current flowing through its battery enters the battery at higher voltage and exits at lower voltage.
(C) enters the lightbulb at lower voltage and exits at higher voltage. The current flowing through its battery enters the battery at lower voltage and exits at higher voltage.
(D) enters the lightbulb at higher voltage and exits at lower voltage. The current flowing through its battery enters the battery at higher voltage and exits at lower voltage.
Problem 15:
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.
(B) at approximately the same distance from the table, but the heavier ball hits the floor well before the lighter ball
(C) at approximately the same time, but the lighter ball hits considerably farther from the table than the heavier ball.
(D) at approximately the same time, but the heavier ball hits considerably farther from the table than the lighter ball.
Problem 16:
Compared to a pure semiconductor, an n-type semiconductor has some extra electrons and a p-type semiconductor has some missing electrons. Suppose you have two electrically neutral disks, one of n-type semiconductor and one of p-type semiconductor. When you touch the two disks,
(A) no movement of electrons occurs because semiconductors contain no mobile electric charges and cannot conduct electric current.
(B) no movement of electrons occurs because such movement would spoil the electrical neutrality of the two disks.
(C) electrons migrate from the n-type semiconductor to the p-type semiconductor and form a depletion region (a region that resembles pure semiconductor).
(D) electrons migrate from the p-type semiconductor to the n-type semiconductor and form a depletion region (a region that resembles pure semiconductor).
Problem 17:
Two identical children run along a horizontal platform side by side and jump into a swimming pool at the same moment. They both jump equally hard, but one child jumps upward while the other child jumps forward. You watch them fall and see that
(A) the child who jumped upward reaches the water before the child who jumped forward.
(B) the two children reach the water at the same moment and at the same distance from the pool's edge.
(C) the two children reach the water at the same moment and but the child who jumped forward travels farther from the pool's edge than does the other child.
(D) the child who jumped forward reaches the water before the child who jumped upward.
Problem 18:
You are watching children play a game of tug-o-war with a plastic clothesline. The two teams are pulling at opposite ends of the cord and each team is trying to drag the other team into a mud puddle that lies between them. After a few minutes without progress, the team on the left suddenly pulls hard toward the left. The team on the right has anticipated this threat and is able to keep their end of the rope from moving. The left end of the rope stretches toward the left and the rope breaks. Breaking the rope required energy and that energy was provided by
(A) the team on the left.
(B) the team on the right.
(C) neither team. It was instead provided by chemical potential energy in the rope itself.
(D) both teams.
Problem 19:
You are watching a baseball game and the pitcher has just thrown the ball toward the batter at home plate. Neglect any effects due to the air. Once the ball has left the pitcher's hand and is heading forward toward home plate, it experiences
(A) a forward horizontal force that diminishes gradually as the ball approaches home plate.
(B) a forward horizontal force that remains constant all the way to home plate.
(C) a forward horizontal force until it reaches the midpoint of its trip to home plate and then a backward horizontal force for the remainder of its trip.
(D) no horizontal force in the forward direction.
Problem 20:
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) while the correct amount of current flows through the hairdryer's heating element, that current alternates too rapidly and overheats the heating element.
(B) the temperature of 230 volt alternating current is much higher than the hairdryer was designed to handle and it burns up the hairdryer.
(C) the electric field in the hairdryer's heating element is too strong and that field pushes too much current through the heating element.
(D) while the correct amount of current flows through the hairdryer's heating element, that current produces too many volts in the heating element and burns it up.
Problem 21:
By themselves, two ordinary steel paperclips do not attract one another magnetically. If you pick up one paperclip with a strong permanent magnet, however, the free end of that paperclip will be able to pick up a second paperclip. What has changed in the first paperclip that now allows it to pick up the second paperclip?
(A) The paperclip originally had no current flowing in its wire, but the nearby permanent magnet induced current in the wire and turned it into an electromagnet.
(B) The paperclip's many magnetic domains originally pointed in random direction, but the nearby permanent magnet has aligned the domains and thereby magnetized the paperclip.
(C) The paperclip originally had zero magnetic pole, but the nearby permanent magnetic attracted magnetic pole into the paperclip so that it now has a non-zero net magnetic pole.
(D) The paperclip originally had no magnetic domains, but the nearby permanent magnet produced magnetic domains in the steel and thereby magnetized the paperclip.
Problem 22:
The electric power grid in the United States uses alternating current because
(A) an alternating current carries more electric power than a direct current.
(B) alternating current is less likely to cause an electrical fire than direct current.
(C) transformers can move power from one circuit to another only if those circuits are carrying alternating current.
(D) an alternating current delivers both positive and negative charges, while a direct current delivers only positive charges. That difference makes alternating current twice as efficient as direct current.
Problem 23:
The power adapter for your clock radio contains a transformer, several diodes, and a capacitor. The purpose of the diodes is to convert
(A) high-voltage alternating current into low-voltage alternating current.
(B) low-voltage direct current into low-voltage alternating current.
(C) low-voltage alternating current into low-voltage direct current.
(D) high-voltage direct current into low-voltage direct current.
Problem 24:
You shoot a free throw at the basketball court and the ball travels in an arc toward the hoop. Neglecting any effects due to the air, the net force on the ball when it is midway between you and the hoop
(A) points up and away from you.
(B) is zero.
(C) points straight down.
(D) points down and away from you.
Problem 25:
Radio and microwave devices use tank circuits to help them move enough electric charge to produce strong electromagnetic waves. At its most basic level, a tank circuit consists of a capacitor (two surfaces that can store separated electric charge) and an inductor (an electromagnet that can carry current). When a tank circuit is helping a device produce an electromagnetic wave,
(A) energy in the tank circuit is shifting back and forth rhythmically between the capacitor's electric field and the inductor's magnetic field.
(B) the tank circuit carries current only in one direction so that the current flows up the antenna and becomes an electromagnetic wave.
(C) the tank circuit is turning AC electric power into DC electric power and thereby strengthening the electromagnetic wave.
(D) the tank circuit is accelerating up and down rhythmically, in sync with the electromagnetic wave.
Problem 26:
You are dragging an old carpet across the floor in a straight line at a steady speed. Which of the following statements about the forces acting on the carpet is correct?
(A) The amount of force that you're exerting on the carpet must be equal to the amount of force that friction is exerting on it.
(B) The amount of force that you're exerting on the carpet must be more than the amount of its weight.
(C) The amount of force that you're exerting on the carpet must be more than the amount of force that friction is exerting on it.
(D) If you were to exert twice as much force on the carpet, it would slide across the floor twice as fast.
Problem 27:
You accidentally leave a thick metal spoon in a glass bowl of soup that you put in the middle of a microwave oven. When you turn on the microwave oven,
(A) sparks shoot out of the spoon toward the top of the oven's cooking chamber.
(B) the spoon becomes radioactive, so that it should be discarded where no one will come into contact with it.
(C) nothing unusual happens because the spoon is a good electrical conductor and has smooth ends.
(D) the spoon becomes extremely hot and scorches the soup in only a few second.
Problem 28:
The difference between a metal and an insulator lies in their band structures. An insulator is unable to conduct electric current in response to an electric field because
(A) its band structure prevents its electrons from crossing the mid-point of the material without becoming positively charged.
(B) all of its electrons reside in filled bands and thus can't shift into empty levels so as to move across the material.
(C) its band structure prevents it from becoming electrically charged, as it must do in order to conduct current.
(D) its band structure puts the guitars on the left and the drums on the right, so there is no room for the lead vocal.
Problem 29:
You have a typical motor/generator, consisting of a rotating permanent magnet and a stationary coil of wire. There is a crank attached to the rotating magnet and you are exerting a torque on that crank. The device acts as
(A) a generator when you twist it in the direction of its rotation and it acts as a motor when you twist it opposite the direction of its rotation.
(B) a motor when you twist it in the direction of its rotation and it acts as a generator when you twist it opposite the direction of its rotation.
(C) a generator.
(D) a motor.
Problem 30:
You are listening to an AM radio station as you drive across the plains of Kansas. It is so flat that you can see the station's vertical transmitting antenna, even though that antenna is 10 miles north of you. 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.
(B) horizontally north and south and its magnetic field points horizontally east and west.
(C) vertically up and down and its magnetic field points horizontally east and west.
(D) horizontally east and west and its magnetic field points horizontally north and south.