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physics
college physics a strategic approach 2nd

College Physics A Strategic Approach 2nd Edition Randall D. Knight, Brian Jones, Stuart Field - Solutions

What is the energy of a Bohr hydrogen atom with a 5.18 nm diameter?
What is the wavelength of the series limit (i.e., the shortest possible wavelength) of the Lyman series in hydrogen?
A simple atom has only two absorption lines, at 250 nm and 600 nm. What is the wavelength of the one line in the emission spectrum that does not appear in the absorption spectrum?
A simple atom has four lines in its absorption spectrum. Ignoring any selection rules, how many lines will it have in its emission spectrum?
A 2.55 eV photon is emitted from a hydrogen atom. What are the Balmer formula n and m values corresponding to this emission?
A 1.00 mW helium neon-laser emits a visible laser beam with a wavelength of 633 nm. How many photons are emitted per second?
An electron with a kinetic energy of 3.90 eV collides with a sodium atom. What possible wavelengths of light are subsequently emitted?
A 1000 W carbon dioxide laser emits an infrared laser beam with a wavelength of 10.6 μm. How many photons are emitted per second?
What is the minimum wavelength of light that can excite the 4s state of sodium?
Hydrogen gas absorbs light of wavelength 103 nm. After- ward, what wavelengths are seen in the emission spectrum?
An electron with a speed of 5.00 × 106 m/s collides with an atom. The collision excites the atom from its ground state (0 eV) to a state with an energy of 3.80 eV. What is the speed of the electron after the collision?
Which has higher energy: an electron in the 4f state or an electron in the 7s state? Explain.
An insulated copper wire is wrapped around an iron nail. The resulting coil of wire consists of 240 turns of wire that cover 1.8 cm of the nail, as shown in Figure P24.57. A current of 0.60 A passes through the wire. If the ferromagnetic properties of the nail increase the field by a factor of 100,
How does the kinetic energy of the particle in Figure P24.62 change as it traverses the velocity selector?A. The kinetic energy increases. B. The kinetic energy does not change. C. The kinetic energy decreases. FIGURE P24.62 в .
The world's strongest magnet can produce a steady field of 45 T. If a circular wire loop of radius 10 cm were held in this magnetic field, what current would be induced in the loop?
Parts a through f of Figure Q25.3 show one or more metal wires sliding on fixed metal rails in a magnetic field. For each, determine if the induced current is clockwise, counterclockwise, or is zero.Figure Q25.3. (a) (c) (e) € X X X X X (b) (d) (f) 11 X X B=0 X X X X X
The rapid vibration accompanying the swimming motions of mayflies has been measured by gluing a small magnet to a swimming mayfly and recording the emf in a small coil of wire placed nearby. Explain how this technique works.
The power lines that run through your neighborhood carry alternating currents that reverse direction 120 times per second. As the current changes, so does the magnetic field around a line. Suppose you wanted to put a loop of wire up near the power line to extract power by "tapping" the magnetic
The magnetic flux passing through a coil of wire varies as shown in Figure Q25.8. During which time interval(s) will an induced current be present in the coil? Explain. 1/2 FIGURE Q25.8 1
Cars on the "Tower of Doom" carnival ride are dropped from a great height, giving riders a few seconds of free fall. To stop the cars, strong permanent magnets attached to the bottoms of the cars pass very close to aluminum vanes sticking up from the bottom of the track. Explain how this braking
A conducting loop around a region of strong magnetic field contains two light bulbs, as shown in Figure Q25.17. The wires connecting the bulbs are ideal. The magnetic field is increasing rapidly. a. Do the bulbs glow? Why or why not? b. If they glow, which bulb is brighter? Or are they equally
A magnet dropped through a clear plastic tube accelerates as expected in free fall. If dropped through an aluminum tube of exactly the same length and diameter, the magnet falls much more slowly. Explain the behavior of the second magnet.
Two polarizers are oriented with axes at 90°, so no light passes through the pair. A piece of plastic is placed between the two. If the plastic is stressed, by being squeezed, light that passes through the first polarizer and the plastic now passes through the second polarizer. The dark and light
Though sunlight is unpolarized, the light that reflects from smooth surfaces may be partially polarized in the direction parallel to the plane of the reflecting surface. How should the long axis of the polarizing molecules in polarized sunglasses be oriented-vertically or horizontally to reduce the
Old-fashioned roof-mounted television antennas were designed to pick up signals across a broad frequency range. Explain why these antennas had metal bars of many different lengths.
The intensity of a beam of light is increased but the light's frequency is unchanged. As a result, which of the following (per-haps more than one) are true? Explain. A. The photons travel faster. B. Each photon has more energy. C. The photons are larger. D. There are more photons per second.
The frequency of a beam of light is increased but the light's intensity is unchanged. As a result, which of the following (perhaps more than one) are true? Explain. A. The photons travel faster. B. Each photon has more energy. C. There are fewer photons per second. D. There are more photons per
Arc welding uses electric current to make an extremely hot electric arc that can melt metal. The arc emits ultraviolet light that can cause sun- burn and eye damage if a welder is not wearing protective gear. Why does the arc give off ultraviolet light?
A spacecraft in orbit around the moon measures its altitude by reflecting a pulsed 10 MHz radio signal from the surface. If the spacecraft is 10 km high, what is the time between the emission of the pulse and the detection of the echo?A. 33 ns B. 67 ns C. 33 μs D. 67 μs
A 6.0 mW vertically polarized laser beam passes through a polarizing filter whose axis is 75° from vertical. What is the laser-beam power after passing through the filter? A. 0.40 mW B. 1.0 mW C. 1.6 mW D. 5.6 mW
A1 x 10-3 m-3 chunk of material has a mass of 3 kg. a. What is the material's density? b. Would a 2 x 10-3 m3 chunk of the same material have the same mass? Explain. c. Would a 2 x 10-3 m3 chunk of the same material have the same density? Explain.
In the circuit shown in Figure Q23.6, bulbs A and B are glowing. Then the switch is closed. What happens to each bulb? Does it get brighter, stay the same, get dimmer, or go out? Explain. 常 ② A FIGURE Q23.6 B ②
One way to find out if a wire has corroded is to measure its resistance. Explain why the resistance of a wire increases if it becomes corroded.
The current in a circuit with only one battery is 2.0 A. Figure P23.9 shows how the potential changes when going around the circuit in the clockwise direction, starting from the lower left corner. Draw the circuit diagram. V (V) 6 4 2 0 Position FIGURE P23.9
The three bulbs in Figure Q23.13 are identical. Rank the bulbs from brightest to dimmest. Explain. A FIGURE Q23.13 с B
An 80-cm-long wire is made by welding a 1.0-mm-diameter, 20-cm-long copper wire to a 1.0-mm-diameter, 60-cm-long iron wire. What is the resistance of the composite wire?
The four bulbs in Figure Q23.14 are identical. Rank the bulbs from brightest to dimmest. Explain. D e B FIGURE Q23.14
You have a collection of 1.0 kΩ resistors. How can you connect four of them to produce an equivalent resistance of 0.25 kΩ?
Figure Q23.15 shows five identical bulbs connected to a battery. All the bulbs are glowing. Rank the bulbs from brightest to dimmest. Explain. Switch FIGURE Q23.23 (2) Bulb A Bulb B (e)
A voltmeter is (incorrectly) inserted into a circuit as shown in Figure Q23.20.Figure Q23.20. a. What is the current in the circuit? b. What does the voltmeter read? c. How would you change the circuit to correctly connect the voltmeter to measure the potential difference across the resistor?
You have six 1.0 kΩ resistors. How can you connect them to produce a total equivalent resistance of 1.5 kΩ?
What are the resistance R and the emf of the battery in Figure P23.23? 3.0 A FIGURE P23.23 R 2.0 A wwwwwww 10 2
A charged capacitor could be connected to two identical resistors in either of the two ways shown in Figure Q23.25. Which configuration will discharge of the capacitor in the shortest time once the switch is closed? Explain.Figure Q23.25. (a) R ww R www (b) RCR wWwwWw.
A flashing light is controlled by the charging and discharging of an RC circuit. If the light is flashing too rapidly, describe two changes that you could make to the circuit to reduce the flash rate.
In the circuit of Figure P23.28, what are the values of ΔV14, ΔV 24, and ΔV 34? FIGURE P23.28 10 V Μ 500 Μ 5.0Ω 5.00 Μ 10 Ω Μ 10 Ω 3 Μ 50Ω
A device to make an electrical measurement of skin moisture has electrodes that form two plates of a capacitor; the skin is the dielectric between the plates. Adding moisture to the skin means adding water, which has a large dielectric constant. If a circuit repeatedly charges and discharges the
For the circuit shown in Figure P23.29, find the current through and the potential difference across each resistor. Place your results in a table for ease of reading. 12 V 3.002 ww ww 16 Ω ww FIGURE P23.29 ww *40 Ω 48 Ω
Adding a myelin sheath to an axon results in faster signal propagation. It also means that less energy is required for a signal to propagate down the axon. Explain why this is so.
What is the current in the circuit of Figure Q23.30?A. 1.0 A B. 1.7 A C. 2.S A D. 4.2 A 10 V 4.0 Ω 60 Ω FIGURE Q23.30
Which resistor in Figure Q23.30 dissipates the most power? A. The 4.0 Ω resistor. B. The 6.0 Ω resistor. C. Both dissipate the same power. 10 V 4.0 Ω· 6.02. FIGURE Q23.30
A photoresistor, whose resistance decreases with light intensity, is connected in the circuit of Figure P23.31. a. Draw a circuit diagram to illustrate how you would use a voltmeter and an ammeter to determine the resistance of the photoresistor in this circuit.b. What do the two meters read when
Normally, household lightbulbs are connected in parallel to a power supply. Suppose a 40 W and a 60 W lightbulb are, instead, connected in series, as shown in Figure Q23.32. Which bulb is brighter?A. The 60 W bulb. B. The 40 W bulb. C. The bulbs are equally bright. 120 V 40 W 60 W FIGURE
For the circuit of Figure P23.38, a. What is the equivalent capacitance? b. How much charge flows through the battery as the capacitors are being charged? 12 V 4.0 μF HH FIGURE P23.38 2.0 μF 1.5 μF
If a cell's membrane thickness doubles but the cell stays the same size, how do the resistance and the capacitance of the cell membrane change? A. The resistance and the capacitance would increase. B. The resistance would increase, the capacitance would decrease. C. The resistance would
What is the time constant for the discharge of the capacitor in Figure P23.40? 1.0 pF FIGURE P23.40 1.0 ΚΩ 1.0 ΚΩ wwwwwww
What is the time constant for the discharge of the capacitor in Figure P23.41? 4.0 με FIGURE P23.41 1.0 ΚΩ 1.0 ΚΩ Μ
Capacitors won't hold a charge indefinitely; as time goes on, charge gradually migrates from the positive to the negative plate. We can model this as a discharge of the capacitor through an internal "leakage resistance." A 0.47 F capacitor charged to 2.5 V will initially discharge with a leakage
A cell membrane has a resistance and a capacitance and thus a characteristic time constant. What is the time constant of a 9.0-nm-thick membrane surrounding a 0.040-mm-diameter spherical cell?
Changing the thickness of the myelin sheath surrounding an axon changes its capacitance and thus the conduction speed. A myelinated nerve fiber has a conduction speed of 55 m/s. If the spacing between nodes is 1.0 mm and the resistance of segments between nodes is 25 MΩ, what is the capacitance of
A particular myelinated axon has nodes spaced 0.80 mm apart. The resistance between nodes is 20 MΩ; the capacitance of each insulated segment is 1.2 pF. What is the conduction speed of a nerve impulse along this axon?
To measure signal propagation in a nerve in the arm, the nerve is triggered near the armpit. The peak of the action potential is measured at the elbow and then, 4.0 ms later, 24 cm away from the elbow at the wrist. a. What is the speed of propagation along this nerve? b. A determination of the
How much power is dissipated by each resistor in Figure P23.51?Figure P23.51 R₁ = 120 9.0 V R₂ = 150 www.www
A myelinated axon conducts nerve impulses at a speed of 40 m/s. What is the signal speed if the thickness of the myelin sheath is halved but no other changes are made to the axon?
A real battery is not just an emf. We can model a real 1.5 V battery as a 1.5 V emf in series with a resistor known as the "internal resistance," as shown in Figure P23.54. A typical battery has 1.0Ω internal resistance due to imperfections that limit current through the battery. When there's no
At this instant, the current in the circuit of Figure P23.59 is 20 mA in the direction shown and the capacitor charge is 200 μC. What is the resistance R? R ww 20 uF 가구 20V FIGURE P23.59
When two resistors are connected in parallel across a battery of unknown voltage, one resistor carries a current of 3.2 A while the second carries a current of 1.8 A. What current will be supplied by the same battery if these two resistors are connected to it in series?
What is the equivalent resistance between points a and b in Figure P23.60?Figure P23.60. a 100 2 100 2 100 2 wwwwwwww 100 52 100 2 www.www 100 Ω ww b
A 9.0 V battery is connected to a wire made of three segments of different metals connected one after another: 10 cm of copper wire, then 12 cm of iron wire, then 18 cm of tungsten wire. All of the wires are 0.26 mm in diameter. Find the potential difference across each piece of wire.
You have a device that needs a voltage reference of 3.0 V, but you have only a 9.0 V battery. Fortunately, you also have several 10 kΩ resistors. Show how you can use the resistors and the battery to make a circuit that provides a potential difference of 3.0 V.
The switch in Figure P23.75 has been closed for a very long time.a. What is the charge on the capacitor? b. The switch is opened at t = 0 s. At what time has the charge on the capacitor decreased to 10% of its initial value? Opens at /= 0 s 후 www 602 100V 402 FIGURE P23.75 w 100 2.0 F
The charging circuit for the flash system of a camera uses a 100 μF capacitor that is charged from a 250 V power supply. What is the most resistance that can be in series with the capacitor if the capacitor is to charge to at least 87% of its final volt- age in no more than 8.0 s?
Intermittent windshield wipers use a variable resistor in an RC circuit to set the delay between successive passes of the wipers. A typical circuit is shown in Figure P23.76. When the switch closes, the capacitor (initially uncharged) begins to charge and the potential at point b begins to
A cell has a 7.0-nm-thick membrane with a total membrane area of 6.0 x 10-9 m2. a. We can model the cell as a capacitor, as we have seen. What is the magnitude of the charge on each "plate" when the membrane is at its resting potential of -70 mV? b. How many sodium ions does this charge
When you are in the southern hemisphere, does a compass point north or south?
For a particular scientific experiment, it is important to be completely isolated from any magnetic field, including the earth's field. A 1.00-m-diameter current loop with 200 turns of wire is set up so that the field at the center is exactly equal to the earth's field in magnitude but opposite in
A horseshoe magnet consists of a bar magnet bent into a U-shape, as shown in Figure Q24.5. Sketch the magnetic field lines for a horseshoe magnet. FIGURE Q24.5 N U
Green turtles use the earth's magnetic field to navigate. They seem to use the field to tell them their latitude-how far north or south of the equator they are. Explain how knowing the direction of the earth's field could give this information.
What is the current direction in the wire of Figure Q24.6? Explain. Ⓒ 4 FIGURE Q24.6 Ⓒ
What is the current direction in the wire of Figure Q24.7? FIGURE Q24.7
Some consumer groups urge pregnant women not to use electric blankets, in case there is a health risk from the magnetic fields from the approximately 1 A current in the heater wires.a. Estimate, stating any assumptions you make, the magnetic field strength a fetus might experience. What percentage
Two wires carry currents in opposite directions, as in Figure Q24.9. The field is 2.0mT at a point below the lower wire. What are the strength and direction of the field at point 1 (midway between the two wires) and at point 2 (the same distance above the upper wire as the 2.0 mT point is below the
Since the wires in the walls of your house carry current, you might expect that you could use a compass to detect the positions of the wires. In fact, a compass will experience no deflection when brought near a current-carrying wire because the current is AC (meaning "alternating current"-the
As shown in Figure Q24.10, a uniform magnetic field points upward, in the plane of the paper. A long wire perpendicular to the paper initially carries no current. When a current is turned on in the wire in the direction shown, the magnetic field at point 1 is found to be zero. Draw the magnetic
The small currents in axons corresponding to nerve impulses produce measurable magnetic fields. A typical axon carries a peak current of 0.040 μA. What is the strength of the field at a distance of 1.0 mm?
Two long wires carry currents in the directions shown in Figure Q24.11. One wire is 10 cm above the other. In which direction is the magnetic field at a point halfway between them? FIGURE Q24.11
A solenoid used to produce magnetic fields for research purposes is 2.0 m long, with an inner radius of 30 cm and 1000 turns of wire. When running, the solenoid produces a field of 1.0 T in the center. Given this, how large a current does it carry?
Figure Q24.13 shows a solenoid as seen in cross section. Compasses are placed at points 1 and 2. In which direction will each compass point when there is a large current in the direction shown? Explain. FIGURE Q24.13 2• 000000000000000
If an electron is not moving, is it possible to set it in motion using a magnetic field? Explain.
One long solenoid is placed inside another solenoid with twice the dia- meter but the same length. Each solenoid carries the same current but in opposite directions, as shown in Figure Q24.14. If they also have the same number of turns, in which direction does the magnetic field in the center
A researcher would like to perform an experiment in zero magnetic field, which means that the field of the earth must be cancelled. Suppose the experiment is done inside a solenoid of diameter 1.0 m, length 4.0 m, with a total of 5000 turns of wire. The solenoid is oriented to produce a field that
Determine the magnetic field direction that causes the charged particles shown in Figure Q24.18 to experience the indicated magnetic forces. FIGURE Q24.18 (a) 12 F out of page (b) ✓ v into page
Experimental tests have shown that hammerhead sharks can detect magnetic fields. In one such test, 100 turns of wire were wrapped around a 7.0-m-diameter cylindrical shark tank. A. magnetic field was created inside the tank when this coil of wire carried a current of 1.5 A. Sharks trained by
An electron is moving near a long, current-carrying wire, as shown in Figure Q24.19. What is the direction of the magnetic force on the electron? FIGURE Q24.19
Two positive charges are moving in a uniform magnetic field with velocities, as shown in Figure Q24.20. The magnetic force on each charge is also shown. In which direction does the magnetic field point? FIGURE Q24.20 F N 15
An electron is moving in a circular orbit in the earth's magnetic field directly above the north magnetic pole. Viewed from above, is the rotation clockwise or counterclockwise?
The detector in a mass spectrometer records the number of ions measured at a fixed position as the field is varied. For a sample consisting of a single atomic species, two peaks were found where one was expected, as shown in Figure Q24.23. The most likely explanation is that the atoms received
An electromagnetic flowmeter applies a magnetic field of 0.20 T to blood flowing through a coronary artery at a speed of 15 cm/s. What force is felt by a chlorine ion with a single negative charge?
A proton is moving near a long, current-carrying wire. When the proton is at the point shown in Figure Q24.24, in which direction is the force on it? Wire V Proton FIGURE Q24.24
A proton is moving near a long, current-carrying wire. When the proton is at the point shown in Figure Q24.25, in which direction is the force on it? Wire 12 Proton FIGURE Q24.25
A long wire and a square loop lie in the plane of the paper. Both carry a current in the direction shown in Figure Q24.26. In which direction is the net force on the loop? Explain.Figure Q24.26. L 7 X

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