1010, Fall 2003, YELLOW Exam 3
Write your name and ID on both your exam and your scantron answer sheet.
Write the color of your exam paper on the top of your scantron sheet next to your name.
Be sure to turn your exam in to the proper box.
Return both the answer sheet and the exam.
This test is closed book, but you may use three 3x5 cards with your own notes
written on them. You may also use a calculator. The exam is worth 30 pts
total.
Conversions you may or may not need:
1 pound = 4.45
N, 1 slug = 14.594 kg, 1 mph = 0.447 m/s. 1 kPa = 1,000 Pascals
The velocity of sound in air is 331 m/s.
The density of water is 1000 kg/m3
Boltzmann’s constant (s)= 5.67 x 10-8 J/(s m2 K4)
6 x 1018 electrons = 1 Coulomb of negative charge
Coulomb’s constant (k) = 8.99 x 109 N m2 / C2
Multiple Choice and True/False Questions: 20 pts total
1 – 2. Your TV uses 1000 watts of power when it is plugged into the 120 V outlet.
1. How much current is flowing along the wire leading from the outlet prong to the TV?
a. 120,000 amps; b. 1000 amps; c. 120 amps; d. 8.3 amps; e. 0.12 amps
2. The amount of current flowing along the wire leading out of the TV and back into the wall socket is:
a. less than the current flowing through the wire leading into the TV;
b. the same as the current flowing through the wire leading into the TV;
c. more than the current flowing through the wire leading into the TV;
d. you need to know more about the electrical circuit of the TV to tell.
3 – 4. You have two light bulbs, Ace "A" and Cheapo "C". The bulbs are identical in every way, except
bulb "A" operates at a temperature of 5000 Kelvin and bulb "C" operates at 2500 Kelvin.
3. How does the amount of power radiated by “A” compare to the power radiated by “B”?
A. Bulb “A” and “B” radiate the same power.
B. Bulb “A” radiates 2 times more power.
C. Bulb “A” radiates 4 times more power.
D. Bulb “A” radiates 16 times more power.
E. Bulb “A” radiates 32 times more power.
4. How does the Spectrum (power vs color) of “A” compare to the Spectrum of “B”?
A. The spectrum of both bulbs is totally invisible to the human eye.
B. The spectrum of “A” is shifted towards the shorter wavelengths (towards the blue end of the wavelength scale) compared to “B”
C. The spectrum of “A” is shifted towards the longer wavelengths (towards the
infrared end of the wavelength scale) compared to “B”
D. The spectra of both bulbs is essentially the same (same colors emitted, both
look the same).
5. You have a flashlight with four 1.5 V batteries connected end-to-end in the normal fashion with the positive terminals all oriented in the same direction and a bulb that has a resistance of 20 ohms. How much electrical power goes into heating up the filament of the bulb?
A. 0.11 watts; B. 30 watts; C. 1.8 watts; D. 6.0 watts; E. 12 watts;
6-8. (True/False) I hook up a battery and a bulb with two wires as shown below. Which of the following statements are True and which are False?
6. True (a) or False (b) Current will not flow
7. True (a) or False (b) The wires will heat up
8. True (a) or False (b) The voltage at the (+) terminal of the battery is the same as the voltage at the base of the light bulb.
9. A positively charged dust particle is attracted to a negatively charged dust particle.
(You don't know the exact magnitude of either charge: they may be equal, they may not)
As the positive dust particle approaches the negatively charged dust particle, what happens to the electrical force it feels?
(Consider only the period of time before they actually touch)
A. The force stays exactly the same as they approach each other.
B. The force decreases as they approach each other.
C. The force increases as they approach each other.
D. Can't decide between the above choices; it would depend on the specific mass and charges of the two particles.
10. True (a) or False (b) On a clear day, visible light passes through the atmosphere more easily then does infrared light.
11. True (a) or False (b) Greenhouse gases are important in global warming because they help absorb the energy coming in from the sun.
12 – 13. Consider two cases. In Case A, the atmosphere has no greenhouse gases. In Case B, the atmosphere has a substantial amount of greenhouse gases. In both cases, the temperature of the earth’s surface is stable (neither increasing nor decreasing). Consider the following statements:
12. True (a) or False (b) The Earth’s surface emits more electromagnetic radiation in Case B than Case A.
13. True (a) or False (b) The amount of power radiated to
space by the earth is smaller in Case B than Case A.
14. The positive post of a car battery is hooked up to one side of a light bulb, the negative post is hooked to the other side, forming a simple, complete circuit. The bulb glows. Suppose you replace the bulb with a new one with TWICE the resistance. What will the new bulb do?
A. Glow equally brightly.
B. Glow more brightly.
C. Glow less brightly.
15 – 16. You have two initially uncharged dust particles. Each dust particle has a mass of 2.0 x 10-12 kg. They are each 1.0 x 10-4 m in diameter and are 0.001 m apart. You take 10 electrons off of one and put them onto the other.
15. The two dust particles are now
a. attracted to each other; b. repelled by each other; c. neither attracted nor repelled by each other.
16. If the dust particles now exert a force on each other, how big is the force of that on particle exerts on the other particle? (Choose e if no force is acting.)
a. 0.015 N; b. 2.0 x 10-23 N; c. 1.0 x 10-17 N; d. 2.5 x 10-20 N; e. No force is acting.
17. You have a lightening rod that is a ˝ inch x ˝ inch square copper rod that is 10 feet long on the top of your house. It has been working okay, but because there is a big lightening storm predicted, your housemate wants to be safe. He gets 100 identical rods and packs them tightly together to make a 50 inch x 50 inch x 10 feet block and puts it on top of the house in place of the original. Both configurations are shown below:
Example of single
rod configuration: 
Example of multi-rod configuration: 
In terms of preventing lightening from hitting your house, this will work
a. better than the original single rod; b. just as well as the single rod;
c. not as well as the single rod
18. Most of the electromagnetic radiation radiated by the earth’s surface is:
A. in the visible wavelength part of the spectrum because of the temperature of the surface of the earth.
B. in the infrared wavelength part of the spectrum because of the temperature of the surface of the earth.
C. in the infrared
wavelength part of the spectrum because of the composition of the earth’s
surface (water, soil, trees, etc).
D. in the visible wavelength part of the spectrum because otherwise we wouldn’t
be able to see the surface of the earth as we can.
19. A large dust particle is sitting on a metal plate in an air cleaner when –1.0 x 10-7 C of extra charge is squirted onto it causing it to move from the first plate to a second that is at a voltage 1000 Volts different from the first. If there is no air in the way to slow it down, how much kinetic energy will the dust particle have just before it hits the second plate?
a. 1 x 10-7 J; b. 1 x 10-1 J; c.1 x 10-3 N; d. 1000 J; e. none of the above.
20. An air cleaner is to remove 2 x 10-9 kg soot particles. It starts by putting 2 x 10-9 C of electrons on each particle and then collects them by applying voltage to two plates on each side of the smokestack. Which combination of voltages will remove the soot most rapidly?
a. one plate at 9,500 V and the other at 10,000 V; b. one plate at 0 V and the other at +2000 V;
c. one plate at 0 V and the other at -3000 V; d. one plate at +2000 V and the other at -2000 V;
e. both plates at 20,000 V.