Questions and Answers of College Physics A Strategic Approach 2nd

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
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.
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
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
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
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
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
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
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
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
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
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
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
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
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,
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
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
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
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,
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
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
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
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
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
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?
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
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,
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
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
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
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
At t = 0 s, a proton is moving with a speed of 5.5 x 105 m/s at an angle of 30 from the x-axis, as shown in Figure P24.28. A uniform magnetic field of magnitude 1.50 T is pointing in the positive
The computers that control MRI machines cannot have CRT monitors. Explain why this is so.
A Slinky is a child's toy that is a long coil spring. Suppose you take a Slinky and let it hang down and stretch out so that the coils do not touch each other, as in Figure Q24.28. Now you connect
Early black-and-white television sets used an electron beam to draw a picture on the screen. The electrons in the beam were accelerated by a voltage of 3.0 kV; the beam was then steered to different
A solenoid carries a current that produces a field inside it. A wire carrying a current lies inside the solenoid, at the center, carrying a current along the solenoid's axis. Is there a force on this
You want to make an electromagnet by wrapping wire around a nail. Should you use bare copper wire or wire coaled with inslIlating plastic? Explain.
The moon does not have a molten iron core like the earth, but the moon does have a small magnetic field. What might be the source of this field?
Archaeologists can use instruments that measure small variations in magnetic field to locate buried walls made of fired brick, as shown in Figure Q24.32. When fired, the magnetic moments in the clay
The unit of current, the ampere, is defined in terms of the force between currents. If two 1.0-meter-long sections of very long wires a distance 1.0 m apart each carry a current of 1.0 A, what is the
A uniform 2.5 T magnetic field points to the right. A 3.0-m-long wire, carrying 15 A, is placed at an angle of 30 to the field, as shown in Figure 24.33. What is the force (magnitude and direction)
The four wires in Figure P24.34 are tilted at 20° with respect to a uniform 0.35 T field. If each carries 4.5 A and is 0.35 m long, what is the force (direction and magnitude) on each? FIGURE
Magnetic information on hard drives is accessed by a read head that must move rapidly back and forth across the disk. The force to move the head is generally created with a voice coil actuator, a
A current loop in a motor has an area of 0.85 cm2 It carries a 240 mA current in a uniform field of 0.62 T. What is the magnitude of the maximum torque on the current loop?
Figure P24.38 shows two square current loops. The loops are far apart and do not interact with each other.a. Use force diagrams to show that both loops are in equilibrium, having a net force of zero
Figure Q24.36 shows four particles moving to the right as they enter a region of uniform magnetic field, directed into the paper as noted. All particles move at the same speed and have the same
If two compasses are brought near enough to each other, the magnetic fields of the compasses themselves will be larger than the field of the earth, and the needles will line up with each other. Which
Moving a charge from point A, where the potential is 300 V, to point B, where the potential is 150 V, takes 4.5 x 10-4 J of work. What is the value of the charge?
The graph in Figure P21.2 shows the electric potential energy as a function of separation for two point charges. If one charge is +0.44 nC, what is the other charge? FIGURE P21.2 0 1 2 3 4 5 6 7 8 9
By moving a 10 nC charge from point A to point B, you determine that the electric potential at B is 150 V. What would be the potential at B if a 20 nC charge were moved from A to B?
Why is the potential energy of two opposite charges a negative number?
It takes 3.0 μJ of work to move a 15 nC charge from point A to B. It takes -5.0 μJ of work to move the charge from C to B. What is the potential difference Vc-VA?
A 20 nC charge is moved from a point where V = 150 V to a point where V = -50 V. How much work is done by the force that moves the charge?
The graph in Figure Q21.6 shows the electric potential along the x-axis. Draw a graph of the potential energy of a 0.10 C charged particle in this region of space, providing a numerical scale on the
At one point in space, the electric potential energy of a 15 nC charge is 45 μJ.a. What is the electric potential at this point? b. If a 25 nC charge were placed at this point, what would its
An electron has been accelerated from rest through a potential difference of 1000 V. a. What is its kinetic energy, in electron volts? b. What is its kinetic energy, in joules? c. What is its
A proton has been accelerated from rest through a potential difference of -1000 V. a. What is its kinetic energy, in electron volts? b. What is its kinetic energy, in joules? c. What is its speed?
Rank in order, from most positive to most negative, the electric potentials V1 to V5 at points 1 to 5 in Figure Q21.10. Explain. 3 FIGURE Q21.10
What potential difference is needed to accelerate a He+ ion (charge +e, mass 4 u) from rest to a speed of 1.0 × 106 m/s?
The electric potential at a point that is halfway between two identical charged particles is 300 V. What is the potential at a point that is 25% of the way from one particle to the other?
Rank in order, from largest to smallest, the electric field strengths E1, E2, E3, and E4 at the four labeled points in Figure Q21.14. Explain. 10 V 20 V 30 V 2 40 V OV FIGURE Q21.14 -10 V -20 V -30
A 2.0 cm × 2.0 cm parallel-plate capacitor has a 2.0 mm spacing. The electric field strength inside the capacitor is 1.0 × 105 V/m.a. What is the potential difference across the capacitor? b. How
a. In Figure P21.14, which capacitor plate, left or right, is the positive plate?b. What is the electric field strength inside the capacitor? c. What is the potential energy of a proton at the
A +25 nC charge is at the origin. a. What are the radii of the 1000 V, 2000 V, 3000 V, and 4000 V equipotential surfaces? b. Draw an equipotential map in the xy-plane showing the charge and these
Rank in order, from largest to smallest, the energies (Uc)1, to (Uc)4 stored in each of the capacitors in Figure Q21.17. Explain. ΔΙ FIGURE Q21.17 C/2 24V +++++ 2C AV AC AV
A 1.0 nC positive point charge is located at point A in Figure Q21.20. The electric potential at point B is A. 9.0 V B. 9.0sin 30° V C. 9.0cos 30° V D. 9.0tan 30° V A 1.0 m 30° B FIGURE Q21.20
A 1.0-mm-diameter ball bearing has 2.0 x 109 excess electrons. What is the ball bearing's potential?
In Figure P21.21, the electric potential at point A is -300 V. What is the potential at point B, which is 5.0 cm to the right of A? E = 1200 V/m A B 30⁰ FIGURE P21.21
One standard location for a pair of electrodes during an EKG is shown in Figure P21.25. The potential difference ΔV31 = V3 - V1 is recorded. For each of the three instants a, b, and c during the
Two 2.0 cm × 2.0 cm square aluminum electrodes, spaced 0.50 mm apart, are connected to a 100 V battery. a. What is the capacitance? b. What is the charge on the positive electrode?
An uncharged capacitor is connected to the terminals of a 3.0 V battery, and 6.0 μC flows to the positive plate. The 3.0 V battery is then disconnected and replaced with a 5.0 V battery, with the
An atom of helium and one of argon are singly ionized-one electron is removed from each. The two ions are then accelerated from rest by the electric field between two plates with a potential
What is the voltage of a battery that will charge a 2.0 μF capacitor to ± 48 μC?
Two electrodes connected to a 9.0 V battery are charged to ± 45 nC. What is the capacitance of the electrodes?
A science-fair radio uses a homemade capacitor made of two 35 cm x 35 cm sheets of aluminum foil separated by a 0.25-mm-thick sheet of paper. What is its capacitance?
Initially, the switch in Figure P21.33 is open and the capacitor is uncharged. How much charge flows through the switch after the switch is closed? FIGURE P21.33 Switch- + 1.5V 루 10 F
A 1.2 nF parallel-plate capacitor has an air gap between its plates. Its capacitance increases by 3.0 nF when the gap is filled by a dielectric. What is the dielectric constant of that dielectric?
A 25 pF parallel-plate capacitor with an air gap between the plates is connected to a 100 V battery. A Teflon slab is then inserted between the plates and completely fills the gap. What is the change
Two 2.0-cm-diameter electrodes with a 0.10-mm-thick sheet of Teflon between them are attached to a 9.0 V battery. Without disconnecting the battery, the Teflon is removed. What are the charge,

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