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physics
electricity and magnetism
Physics Principles with Applications 7th edition Douglas C. Giancoli - Solutions
Eight 7.0-W Christmas tree lights are connected in series to each other and to a 110-V source, what is the resistance of each bulb?
During an action potential, Na+ ions move into the cell at a rate of about 3 X 10-7 mol/m2 ∙ s. How much power must be produced by the “active Na+ pumping” system to produce this flow against a+ 30-mV potential difference? Assume that the axon is 10cm long and 20μm in diameter.
A close inspection of an electric circuit reveals that a 480-Ω resistor was inadvertently soldered in the place where a 320-Ω resistor is needed. How can this be fixed without removing anything from the existing circuit?
Determine(a) The equivalent resistance of the circuit shown in fig. 19-39, and(b) The voltage across each resistor.
How many coulombs are there in 1.00 ampere-hour?
What is the average current drawn by a 1.0-hp 120-V motor? (1 hp = 746 W.)
A 75-W, 110-V bulb is connected in parallel with a 40-W, 110-V bulb. What is the net resistance?
A person accidentally leaves a car with the lights on. If each of the two headlights uses 40W and each of the two taillights 6.W, for a total of 92W, how long will a fresh 12-V battery last if it if rated at 95 A ∙ h? Assume the full 12 V appears across each bulb.
Consider the network of resistor shown in Fig. 19-40. Answer qualitatively:(a) What happens to the voltage across each resistor when the switch S is closed?(b) What happens to the current through each when the switch is closed?(c) What happens to the power output of the battery when the switch is
The heating element of a 110-V, 1500-W heater is 5.4 m long. If it is made of iron, what must its diameter be?
What is the net resistance of the circuit connected to the battery in Fig. 19-41? Each resistance has R = 2.8k Ω.
The conductance G of an object is defined as the reciprocal of the resistance R; that is, G = 1/R. The unit of conductance is a mho (= ohm-1), which is also called the siemens (S). What is the conductance (in siemens) of an object that draws 730 mA of current at 3.0V?
A small city requires about 10 MW of power. Suppose that instead of suing high-voltage lines to supply the power, the power is delivered at 120V. Assuming a two wire line of 0.50-cm-diamter copper wire, estimate the cost of the energy lost to heat per hour per meter. Assume the cost of electricity
(a) A particular household uses a 1.8-kW heater 3.0 h/day (“on” time), four 100-W lightbulbs 6.0 h/day, a 3.0-kW electric stove element for a total of 1.4 h/day, and miscellaneous power amounting to 2.0 kWh/day if electricity costs $0.105 per kWh, what will be their monthly bill (30 d)?(b) How
Three equal resistors (R) are connected to a battery as shown in Fig. 19-42. Qualitatively, what happens to?(a) The voltage drop across each of this resistor,(b) The current flow through each,(c) The terminal voltage of the battery, when the switch S is opened, after having been closed for a long
A length of wire is cut in half and the two lengths are wrapped together side by side to make a thicker wire. How does the resistance of this new combination compare to the resistance of the original wire?
A 2.8-kΩ and a 2.1-kΩ resistor are connected in parallel; this combination is connected in series with a 1.8-kΩ resistor. If each resistor is rated 1\2 W) maximum without overheating), what is the maximum voltage that can be applied across the whole network?
A 1200-W hair dryer is designed for 117V.(a) What will be the percentage change in power output if the voltage drops to 105 V? Assume no change in resistance.(b) How would the actual change in resistivity with temperature affect your answer?
Calculate the current in the circuit of Fig. 19-43 and show that the sum of all voltage changes around the circuit is zero.
The wiring in a house must be thick enough so it does not become so hot as to start a fire. What diameter must a copper wire be if it is to carry a maximum current of 35 A and produce no more than 1.8W of heat per meter of length?
Determine the terminal voltage of each battery in Fig. 19-44.
Suppose a current is given by the equation l = 1.80sin 210r, where l is in amperes and t in seconds. (a) What is the frequency? (b) What is the rms value of the current? (c) If this is the current through a 42.0-Ω resistor, write the equation that describes the voltage as a function of
(a) What is the potential difference between points a and d in Fig. 19-45 (same circuit as Fig. 19-13, Example 19-8),(b) What is the terminal voltage of each battery?
A microwave oven running at 65% efficiency delivers 950 W of energy per second to the interior. Find (a) The power drawn from the source, and (b) The current drawn. Assume a source voltage of 120V..
For the circuit shown in Fig. 19-46, find the potential difference between points a and b, each resistor has R = 75Ω and each battery is 1.5V.
A 1.00-Ω wire is stretched uniformly to 3.00 times its original length. What is its resistance now?
Determine the magnitude and direction of the currents through R1 and R2 in Fig 19-47.
220 V is applied to two different conductors made of the same material. One conductor is twice as long and twice the diameter of the second. What is the ratio of the power transformed in the first relative to the second?
Repeat problem 27, now assuming that each battery has an internal resistance r = 1.2Ω
An electric heater is used to heat a room of volume 62m3. Air is brought into the room at 5oC and is completely replaced twice per hour. Heat loss through the walls amounts to approximately 850kcal/h. If the air is to be maintained at 20oC, what minimum wattage must the heater have? (The specific
A 2200-W oven is hooked to a 240-V source. (a) What is the resistance of the oven? (b) How long will it take to bring 120mL of 15oC water to 100oC assuming 75% efficiency? (c) How much will this cost at 11 cents/kWh?
Determine the magnitudes and directions of the currents in each resistor shown if Fig. 19-48. The batteries have emfs of ε1 = 9.0 V and ε2 = 12.0 V and the resistors have values of R1 = 25Ω, R2 = 18Ω, and R3 = 35Ω.
(a) Determine the horsepower required. (b) After approximately how many kilometers must the batteries be recharged?
Repeat problem 29, assuming each battery has internal resistance r = 1.0Ω.
A 12.5-Ω resistor is made from a coil of copper wire whose total mass is 18.0g. What is the diameter of the wire, and how long is it?
Calculate the currents in each resistor of Fig. 19-49.
(a) Determine the currents l1, l2, and l3 in Fig. 19-50. Assume the internal resistance of each battery is r = 1.0Ω.(b) What is the terminal voltage of the 6.0-V battery?
What would the current l1, be in Fig .19-50 if the 12-Ω resistor is shorted out? Let r = 1.0Ω.
Suppose two batteries, with unequal emfs of 2.00 V and 3.00 V, are connected as shown in Fig. 19-51. If each internal resistance is r = 0.100 Ω, and R = 4.00Ω, what is the voltage across the resistor R?
(a) Six 4.7-μF capacitors are connected in parallel. What is the equivalent capacitance? (b) What is their equivalent capacitance if connected in series?
You have three capacitors, of capacitance 3200 pF, 7500pF, and 0.0100μF. What maximum and minimum capacitance can you form from these? How do you make the connection in each case?
A 3.00-μF and a 4.00-μF capacitor are connected in series, and this combination is connected in parallel with a 2.00-μF capacitor (see Fig. 19-52). What is the net capacitance?
If 26.0 V is applied across the whole network of Fig. 19-52, calculate the voltage across each capacitor.
The capacitance of a portion of a circuit is to be reduced from 4800pF to 2900pF. What capacitance can be added to the circuit to produce this effect without removing existing circuit elements? Must any existing connections be broken in the process?
An electric circuit was accidentally constructed using a 5.0-μF capacitor instead of the required 16-μF value. Without removing the 5.0-μF capacitor, what can a technician add to correct this circuit?
Determine the equivalent capacitance of the circuit shown in Fig. 19-53.
In Fig. 19-53, If C1 = C2 = 2C3 = 22.6μF, how much charge is stored on each capacitor when V = 45.0V?
In Fig. 19-53, suppose C1 = C2 = C3 = 16.0 μF. If the charge on C2 is Q2 = 24.0μC, determine the charge on each of the other capacitors, the voltage across each capacitor, and the voltage V across the entire combination.
In Fig. 19-53, let V = 78 V and C1 = C2 = C3 = 7.2μF. How much energy is stored in the capacitor network?
A 0.40-μF and a 0.60-μF capacitor are connected in series to a 9.0-V battery. Calculate (a) The potential difference across each capacitor, and (b) The charge on each. (c) Repeat parts (a) and (b) assuming the two capacitors are in parallel.
Three conducting plates, each of area A, are connected as shown in Fig. 19-54.(a) Are the two capacitors formed connected in series or in parallel?(b) Determine C as function of d1, d2 and A. Assume d1 + d2 is much less than the dimensions of the plates.
A 100-W, 120-V lightbulb has a resistance of 12 Ω when cold (20oC) and 140Ω when on (hot). Calculate its power consumption at. (a) The instant it is turned on, and. (b) After a few moments when it is hot.
A circuit contains a single 250-pF capacitor hooked across a battery. It is desired to store three times as much energy in a combination of two capacitors by adding a dingle capacitor to this one. How would you hook it up, and what would its value be?
The Tevatron accelerator at Fermilab (Illinois) is designed to carry an 11-mA beam of protons traveling at very nearly the speed of light (3.0 X 108 m/s) around a ring 6300 m in circumference. How many protons are stored in the beam?
A 185-pF capacitor is connected in series with an unknown capacitance, and as a series combination they are connected to a battery with and emf of 25.0 V. If the 185-pF capacitor stores 125pC of charge on its plates, what is the unknown capacitance?
An air conditioner draws 12 A at 220-V ac. The connecting cord is copper wire with a diameter of 1.628mm. (a) How much power does the air conditioner draw?(b) If the total length of wire is 15m, how much power is dissipated in the wiring?(c) If no. 12 wire, with a diameter of 2.053mm, was used
A fish-tank heater is rated at 95W when connected to 120V. The heating element is a coil of Nichrome wire. When uncoiled, the wire has a total length of 3.8m. What is the diameter of the wire?
Electrocardiographs are often connected as shown in Fig. 19-55. The leads are said to be capacitively coupled. A time constant of 3.0s is typical and allows rapid changes in potential to be recorded accurately. If C =3.0μF, what value must R have?
In an automobile, the system voltage varies from about 12V when the car is off to about 13.8V when the car is on and the charging system is in operation, a difference of 15%. By what percentage does the power delivered to the headlights vary as the voltage changes from 12 V to 13.8V? Assume the
Lightbulb A is rated at 120 V and 40 W for automotive applications.(a) What is the current through each bulb?(b) What is the resistance of each bulb? (c) In one hour, how much charge passes through each bulb?(d) In one hour, how much energy does each bulb use?(e) Which bulb requires larger diameter
Copper wire of diameter 0.259 cm is used to connect a set of appliances at 120 V, which draw 2250 W of power total. (a) What power is wasted in 25.0m of this wire?(b) What is your answer if wire of diameter 0.412 cm is used?
In Fig.19-56 (same as Fig. 19-20a), the total resistance is 15.0kΩ, and the batterys emf is 24.V. If the time constant is measured to be 35.0μs, calculate (a) The total capacitance of the circuit and (b) The time it takes for the voltage across the resistor to reach 16.0V
A copper pipe has an inside diameter of 3.00cm and an outside diameter of 5.00cm (Fig. 18-37). What is the resistance of 10.0m of this pipe?
If a wire of resistance R is stretched uniformly so that its length doubles, by what factor does the power dissipated in the wire change, assuming it remains hooked up to the same voltage source? Discuss.
The RC circuit of Fig. 19-57 (same as Fig. 19-21a) has R = 6.7 kΩ and C = 3.0μF. The capacitor is at voltage V0 at t = 0, when the switch is closed. How long does it take the capacitor to discharge to 1.0% of its initial voltage?
A tungsten filament used in a flashlight bulb operates at 0.20 A and 3.2 V. If its resistance at 20oC is 1.5Ω, what is the temperature of the filament when the flashlight is on?
A compass needle is not always balance parallel to the Earth’s surface, but one end may dip downward. Explain.
Draw the magnetic field lines around a straight section of wire carrying a current horizontally to the left.
In what direction are the magnetic field lines surrounding a straight wire carrying a current that is moving directly away from you?
A horseshoes magnet is held vertically with the North Pole on the left and South Pole on the right. A wire passing between the poles, equidistant from them, carries a current directly away from you. In what direction is the force on the wire?
Will a magnet attract any metallic object, or only those made of iron? (Try it and see.) What is this so?
Two iron bars attract each other no matter ends are placed close together, Are both magnets? Explain.
The magnetic field due to current in wires in your home can affect a compass. Discuss the effect in terms of currents, including if they are ac or dc.
If a negatively charged particle enters a region of uniform magnetic field which is perpendicular to the particle’s velocity, will the kinetic energy of the particles increase, decrease, or stay the same? Explain your answer. (Neglect gravity and assume there is no electric field.)
In fig. 20-45, charged particles move in the vicinity of a current-carrying wire. For each charged particles, the arrow indicates the direction of motion of the particle, and the + or indicates the sign of the charge, for each of the particles, indicate the direction of the magnetic force due ro
Three particles, a, b, and c, enter a magnetic field as shown in Fig. 20-46, what can you say about the charge on each particle?
A positively charged particle in a no uniform magnetic field follows the trajectory shown in Fig. 20-47. Indicate the direction of the magnetic field everywhere in space, assuming the path is always in the plane of the page, and indicate the relative magnitudes of the field in each region.
Can an iron rod attract a magnet? Can a magnet attract an iron rod? What must you consider to answer these questions?
Explain why a strong magnet held near a CRT television screen (Section. 17-10 causes the picture to become distorted. Also explain why the picture sometimes goes completely black where the field is strongest. [But don’t risk damage to your TV by this.]
Suppose you have three iron rods, two of which are magnetized but the third is not, hot would you determine which two are the magnets without any additional objects?
Can you set a resting electron into motion with a magnetic field with an electric field? Explain.
A charged particle is moving in a circle under the influence of uniform magnetic field. If an electric field that points in the same direction as the magnetic field is turned on, describe the path the charged particle will take.
The force on a particle in a magnetic field is the idea behind electromagnetic pumping. It is used to pump metallic fluids (such as sodium) and to pump blood in artificial heart machines. The basic design is shown in Fig. 20- 48. An electric field is applied perpendicular to a blood vessel and to a
A beam of electron is directed toward a horizontal wire carrying a current from left to right (Fig. 20-49). In what direction is the mean deflected?
Describe electric and/or magnetic field that surround a moving electric charge.
A charged particle moves in a straight line through a particular region of space. Could there be a nonzero magnetic field in this region? If so, give two possible situations.
If a moving charged particle is deflected sideways in some region of space, can we conclude, for certain, that B ≠ 0 in that region? Explain.
In a particular region of space there is a uniform magnetic field B. Outside this region, B = 0. Can you inject an electron from outside into the field perpendicular clearly so that is will move in a closed circular path in the field? What if the electron is injected near the center?
How could you y=tell whether moving electrons in a certain region of space are being deflected by an electric field or by a magnetic field (or by both)?
How can you make a compass without using iron or other ferromagnetic material?
Two long wires carrying equal currents l are at right angles to each other, but don’t quite touch. Describe the magnetic force one exerts on the other.
A horizontal current-carrying wire, free to move in Earth’s gravitational field, is suspended directly above a second, parallel, current-carrying wire,(a) In what direction is the current in the lower wire?(b) Can the upper wire be held in stable equilibrium due to the magnetic force of the lower
Why will either pole of a magnet attract an unmagnetized piece of iron?
An unmagnetized nail will not attract an unmagnetized paper clip. However, if one end of the nail is contact with a magnet, the other end will attract a paper clip. Explain.
Two ions have the same mass, but one is singly ionized and the other is doubly ionized, how will their positions on the film of a mass spectrometer (Fig. 20-39) differ?
What would be the effect on B inside a long solenoid if(a) The diameter of all the loops was doubled,(b) The spacing between loops was doubled or(c) The solenoid’s length was double along with a doubling in the total number of loops?
A type of magnetic switch similar to a solenoid is a relay (Fig. 20-50) a relay is an electromagnet (the iron rod inside the coil does not move? Which, when activated, attracts a piece of iron on a pivot. Design a relay to close an electrical switch. A relay is used when you need to switch on a
(a) What is the magnetic of the force per meter of length on a straight wire carrying as 8.40-A current when perpendicular to a 0.90-T uniform magnetic field?(b) What is the angle between the wire and field is 45.0o?
Calculation the magnitude of the magnetic force on a 160-m length of straight wire stretched between two towers carrying a 150-A current. The earth’s magnetic field of 5.0X 10-5 T makes an angle of 650 with the wire.
How much current is flowing in a wire 4.80m long if the maximum force on it is 0.750N when placed in uniform 0.0800-T field?
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