1. Two waves are created in air and move toward outer space. Wave X cannot travel in the vacuum of outer space, but wave Y can. What types of waves are X and Y ?
2. Which of the following is a correct description of the field diagram shown above?
(A) It shows field vectors for two particles with charges of opposite sign and about the same magnitude, and it could also represent their gravitational field if they have about the same mass.
(B) It shows field vectors for two particles with charges of opposite sign and about the same magnitude, but it could not represent their gravitational field.
(C) It shows field vectors for two particles with charges of the same sign and about the same magnitude, and it could also represent their gravitational field if they have about the same mass.
(D) It shows field vectors for two particles with charges of the same sign and about the same magnitude, but it could not represent their gravitational field.
3. Some students are trying to determine whether the radius of a metal sphere affects the amount of charge that it can hold. The students have metal spheres of different radii and known masses that can be attached to a stand by a string, as shown above. The stand is midway between a set of large plates that are connected to a battery to create a nearly uniform electric field in the region between them and near their centers. The students rub a rod with cloth and touch it to each sphere to charge the sphere, and they observe the deflection of the sphere as it is attracted to one plate. They keep adding charge to each sphere until they cannot observe any change in deflection. Which of the following data will give them information that is useful for quantitatively comparing the amount of charge on each sphere?
(A) The number of times they rub the cloth back and forth on the rod
(B) The number of times they touch the rod to the sphere
(C) The string’s angle of deflection
(D) The string’s direction of deflection
4. What are the value and the direction of the current through the 5 Ω resistor in the circuit shown above?
(A) 1.0 ampere 1.0 ampere toward the top of the page
(B) 1.0 ampere 1.0 ampere toward the bottom of the page
(C) 2.0 amperes 2.0 amperes toward the top of the page
(D) 2.0 amperes 2.0 amperes toward the bottom of the page
Questions 5-7 refer to the following material.
A closed chamber filled with a gas that is modeled as ideal has a movable piston of area A. The graph above of pressure P as a function of volume Vshows three processes that make up cycle XYZX through which the gas is taken. Process ZX is isothermal.
5. During which process is no work done on or by the gas?
(D) Work was done on or by the gas during every process.
6. What is the force exerted on the piston by the gas during process XY?
7. During which process is the amount of work done on the gas equal to the amount of energy that the gas exchanges with its surroundings through heating or cooling?
(D) None of the processes; the amount of work done on the gas is always greater than the amount of energy that the gas exchanges with its surroundings through heating or cooling.
1. (10 points, suggested time 20 minutes)
A student is performing some lab experiments with batteries, ohmic resistors, capacitors, and some identical ohmic lightbulbs.
(a) The student first connects four lightbulbs and an ideal battery as shown above in circuit 1 and observes the brightness of each lightbulb. The student then moves lightbulb C to obtain circuit 2. In a coherent, paragraph-length response, describe how the brightnesses of lightbulbs A and D in circuit 2 compare to their brightnesses in circuit 1. Support your claims with appropriate physics principles.
(b) The student thinks that one of the available batteries has a nonnegligible internal resistance. The student measures the potential difference across the battery as 9 volts when it is not connected to any other circuit elements. The student then connects the circuit shown above, where the battery is represented by the circuit elements in the dashed box. The voltmeter indicates that the potential difference across one resistor is 4 volts. Calculate the internal resistance of the battery.
(c) One of the lightbulbs is now connected with an ideal battery, an open switch, a resistor R and an initially uncharged capacitor C, as shown below. The resistance of the lightbulb and the resistor are about the same. The switch is then closed and left closed for a long time. Describe how, if at all, the brightness of the lightbulb changes during the time the switch remains closed, and explain why.
2. (12 points, suggested time 25 minutes)
A cylinder with a movable piston contains a sample of ideal gas. A temperature probe and a pressure probe are inserted into the cylinder, as shown above. The sample of gas is taken through a three-step cycle, ABCA .
In process AB , the volume is decreased to 1/4 its original value while constant pressure is maintained.
In process BC , the gas expands back to its original volume isothermally.
In process CA , the gas returns to its original state without any work being done on or by the gas.
i On the axes below, draw a graph of pressure P as a function of volume V for the three-step process ABCA , labeling states B and C. The pressure and volume of state A are PA and VA,respectively. Label the axes with the values of pressure and volume for states B and C in terms of PA and VA .
ii For process B C , is energy added to the gas by heating or removed from the gas by cooling? Support your claim using physics principles.
(b) For processC A C A , is the net flow of energy into the gas or out of the gas? Explain your reasoning using physics principles. Describe one method by which this flow of energy could be accomplished in the laboratory.
(c) Curves 1 and 2 below show the distributions of particle speeds when the sample of gas is in two of the states, with curve 1 a state that occurs before curve 2 as the gas goes through the cycle. Which states correspond to curve 1 and 2? Support your claim using physics principles.