The cost of electricity varies widely throughout the United States; $0.120/kWh is a typical value. At this unit price, calculate the cost of (a) Leaving a 40.0 - W porch light on for 2 weeks while you are on vacation, (b) Making a piece of dark toast in 3.00 min with a 970 - W toaster, and (c) Drying a load of clothes in 40.0 min in a 5200 - W dryer.
> A person’s body temperature is 101.6°F, indicating a fever of 3.0°F above the normal average body temperature of 98.6°F. How many degrees above normal is this body temperature on the Celsius scale?
> In a student experiment, a constant-volume gas thermometer is calibrated in dry ice (-78.5°C) and in boiling ethyl alcohol (78.0°C). The separate pressures are 0.900 atm and 1.635 atm. (a) What value of absolute zero in degrees Celsius does the calibrati
> On January 22, 1943, in Spearfish, South Dakota, the temperature rose from -4.00°F to 45.0°F over the course of two minutes (the current world record for the fastest recorded temperature change). By how much did the temperature change on the Kelvin scale
> Death Valley holds the record for the highest recorded temperature in the United States. On July 10, 1913, at a place called Furnace Creek Ranch, the temperature rose to 134°F. The lowest U.S. temperature ever recorded occurred at Prospect Creek Camp in
> Two resistors connected in series have an equivalent resistance of 690 Ω. When they are connected in parallel, their equivalent resistance is 150 Ω. Find the resistance of each resistor.
> Consider the combination of resistors shown in Figure P18.8. a) Find the equivalent resistance between point a and b. (b) If a voltage of 35.0 V is applied between points a and b, find the current in each resistor. Figure P18.8:
> Suppose 9.30 x 105 J of energy are transferred to 2.00 kg of ice at 0°C. (a) Calculate the energy required to melt all the ice into liquid water. (b) How much energy remains to raise the temperature of the liquid water? (c) Determine the final temperatur
> (a) Find the equivalent resistance between points a and b in Figure P18.7. (b) Calculate the current in each resistor if a potential difference of 34.0 V is applied between points a and b. Figure P18.7:
> Three 9.0 - Ω resistors are connected in series with a 12 - V battery. Find (a) The equivalent resistance of the circuit and (b) The current in each resistor. (c) Repeat for the case in which all three resistors are connected in parallel across the batte
> Two resistors, R1 and R2, are connected in series. (a) If R1 = 2.00 Ω and R2 = 4.00 Ω, calculate the single resistance equivalent to the series combination. (b) Repeat the calculation for a parallel combination of R1 and R2.
> A battery with a 0.100 - Ω internal resistance supplies 15.0 W of total power with a 9.00 V terminal voltage. Determine (a) The current I and (b) The power delivered to the load resistor.
> A battery with an emf of 12.0 V has a terminal voltage of 11.5 V when the current is 3.00 A. (a) Calculate the battery’s internal resistance r. (b) Find the load resistance R.
> (a) Find the current in an 8.00 - Ω resistor connected to a battery that has an internal resistance of 0.15 V if the voltage across the battery (the terminal voltage) is 9.00 V. (b) What is the emf of the battery?
> A battery with ε = 6.00 V and no internal resistance supplies current to the circuit shown in Figure P18.14. When the double - throw switch S is open as shown in the figure, the current in the battery is 1.00 mA. When the switch is closed in
> The resistance between terminals a and b in Figure P18.13 is 75 Ω. If the resistors labeled R have the same value, determine R. Figure P18.13:
> Four resistors are connected to a battery as shown in Figure P18.12. (a) Determine the potential difference across each resistor in terms of Ñ”. (b) Determine the current in each resistor in terms of I. Figure P18.12:
> Consider the circuit shown in Figure P18.11. Find (a) The potential difference between points a and b and (b) The current in the 20.0 - Ω resistor. Figure P18.11:
> An unknown substance has a mass of 0.125 kg and an initial temperature of 95.0 °C. The substance is then dropped into a calorimeter made of aluminum containing 0.285 kg of water initially at 25.0 °C. The mass of the aluminum container is 0.150 kg, and th
> Consider the circuit shown in Figure P18.10. (a) Calculate the equivalent resistance of the 10.0 - Ω and 5.00 - Ω resistors connected in parallel. (b) Using the result of part (a), calculate the combined resistance of the 10.0 - &
> A battery having an emf of 9.00 V delivers 117 mA when connected to a 72.0 - Ω load. Determine the internal resistance of the battery.
> An iron wire has a cross - sectional area of 5.00 x 10-6 m2. Carry out steps (a) through (e) to compute the drift speed of the conduction electrons in the wire. (a) How many kilograms are there in 1 mole of iron? (b) Starting with the density of iron and
> An aluminum wire having a cross - sectional area of 4.00 x 10-6 m2 carries a current of 5.00 A. The density of aluminum is 2.70 g/cm3. Assume each aluminum atom supplies one conduction electron per atom. Find the drift speed of the electrons in the wire.
> A 2.0 x 102 - km - long high - voltage transmission line 2.0 cm in diameter carries a steady current of 1.0 x 103 A. If the conductor is copper with a free charge density of 8.5 x 1028 electrons/m3, how many years does it take one electron to travel the
> A man wishes to vacuum his car with a canister vacuum cleaner marked 535 W at 120. V. The car is parked far from the building, so he uses an extension cord 15.0 m long to plug the cleaner into a 120. - V source. Assume the cleaner has constant resistance
> An x - ray tube used for cancer therapy operates at 4.0 MV, with a beam current of 25 mA striking the metal target. Nearly all the power in the beam is transferred to a stream of water flowing through holes drilled in the target. What rate of flow, in ki
> When a straight wire is heated, its resistance changes according to the equation R = R0[1 + α(T - T0)] (Eq. 17.7), where α is the temperature coefficient of resistivity. (a) Show that a more precise result, which includes the
> A resistor is constructed by forming a material of resistivity 3.5 x 105 Ω · m into the shape of a hollow cylinder of length 4.0 cm and inner and outer radii 0.50 cm and 1.2 cm, respectively. In use, a potential difference is applied between the ends of
> In a certain stereo system, each speaker has a resistance of 4.00 Ω. The system is rated at 60.0 W in each channel. Each speaker circuit includes a fuse rated at a maximum current of 4.00 A. Is this system adequately protected against overload?
> A Styrofoam cup holds 0.275 kg of water at 25.0°C. Find the final equilibrium temperature after a 0.100-kg block of copper at 90.0°C is placed in the water. Neglect any thermal energy transfer with the Styrofoam cup.
> A length of metal wire has a radius of 5.00 x 10-3 m and a resistance of 0.100 Ω. When the potential difference across the wire is 15.0 V, the electron drift speed is found to be 3.17 x 10-4 m/s. On the basis of these data, calculate the density of free
> A Nichrome heating element in an oven has a resistance of 8.0 Ω at 20.0°C. (a) What is its resistance at 350°C? (b) What assumption did you have to make to obtain your answer to part (a)?
> A 120. - V motor has mechanical power output of 2.50 hp. It is 90.0% efficient in converting power that it takes in by electrical transmission into mechanical power. (a) Find the current in the motor. (b) Find the energy delivered to the motor by electri
> The current in a conductor varies in time as shown in Figure P17.60. (a) How many coulombs of charge pass through a cross section of the conductor in the interval from t = 0 to t = 5.0 s? (b) What constant current would transport the same total charge du
> If 3.25 x 10-3 kg of gold is deposited on the negative electrode of an electrolytic cell in a period of 2.78 h, what is the current in the cell during that period? Assume the gold ions carry one elementary unit of positive charge.
> You are cooking breakfast for yourself and a friend using a 1.20 - kW waffle iron and a 0.500 - kW coffeepot. Usually, you operate these appliances from a 110. - V outlet for 0.500 h each day. (a) At 12.0 cents per kWh, how much do you spend to cook brea
> A 50.0 - g sample of a conducting material is all that is available. The resistivity of the material is measured to be 11 x 10-8 Ω · m, and the density is 7.86 g/cm3. The material is to be shaped into a solid cylindrical wire that has a total resistance
> An experiment is conducted to measure the electrical resistivity of Nichrome in the form of wires with different lengths and cross - sectional areas. For one set of measurements, a student uses 30.0 - gauge wire, which has a cross - sectional area of 7.3
> Birds resting on high - voltage power lines are a common sight. The copper wire on which a bird stands is 2.2 cm in diameter and carries a current of 50. A. If the bird’s feet are 4.0 cm apart, calculate the potential difference between its feet.
> A particular wire has a resistivity of 3.0 x 10-8 Ω · m and a cross - sectional area of 4.0 x 10-6 m2. A length of this wire is to be used as a resistor that will develop 48 W of power when connected across a 20. - V battery. What length of wire is requi
> When a driver brakes an automobile, the friction between the brake drums and the brake shoes converts the car’s kinetic energy to thermal energy. If a 1500-kg automobile traveling at 30 m/s comes to a halt, how much does the temperature rise in each of t
> A given copper wire has a resistance of 5.00 Ω at 20.0°C while a tungsten wire of the same diameter has a resistance of 4.75 Ω at 20.0°C. At what temperature will the two wires have the same resistance?
> Consider an aluminum wire of diameter 0.600 mm and length 15.0 m. The resistivity of aluminum at 20.0°C is 2.82 x 1028 Ω · m. (a) Find the resistance of this wire at 20.0°C. (b) If a 9.00 - V battery is connected across the ends of the wire, find the cur
> A car owner forgets to turn off the headlights of his car while it is parked in his garage. If the 12.0 - V battery in his car is rated at 90.0 A · h and each headlight requires 36.0 W of power, how long will it take the battery to completely discharge?
> If a battery is rated at 60.0 A · h, how much total charge can it deliver before it goes “dead”?
> A tungsten wire in a vacuum has length 15.0 cm and radius 1.00 mm. A potential difference is applied across it. (a) What is the resistance of the wire at 293 K? (b) Suppose the wire reaches an equilibrium temperature such that it emits 75.0 W in the form
> A certain laboratory experiment requires an aluminum wire of length of 32.0 m and a resistance of 2.50 Ω at 20.0°C. What diameter wire must be used?
> Two wires A and B made of the same material and having the same lengths are connected across the same voltage source. If the power supplied to wire A is three times the power supplied to wire B, what is the ratio of their diameters?
> An office worker uses an immersion heater to warm 250 g of water in a light, covered, insulated cup from 20.°C to 100.°C in 4.00 minutes. The heater is a Nichrome resistance wire connected to a 120 - V power supply. Assume the wire is at 100.°C throughou
> An electric utility company supplies a customer’s house from the main power lines (120. V) with two copper wires, each of which is 50.0 m long and has a resistance of 0.108 Ω per 300. m. (a) Find the potential difference at the customer’s house for a loa
> A student drops two metallic objects into a 120-g steel container holding 150 g of water at 25°C. One object is a 200-g cube of copper that is initially at 85°C, and the other is a chunk of aluminum that is initially at 5.0°C. To the surprise of the stud
> The potential difference across a resting neuron in the human body is about 75.0 mV and carries a current of about 0.200 mA. How much power does the neuron release?
> Batteries are rated in terms of ampere - hours (A · h). For example, a battery that can deliver a current of 3.0 A for 5.0 h is rated at 15 A · h. (a) What is the total energy, in kilowatt - hours, stored in a 12 - V battery rated at 55 A · h? (b) At $0.
> A copper cable is designed to carry a current of 300. A with a power loss of 2.00 W/m. What is the required radius of this cable?
> A certain toaster has a heating element made of Nichrome resistance wire. When the toaster is first connected to a 120. - V source of potential difference (and the wire is at a temperature of 20.0°C), the initial current is 1.80 A but the current begins
> Light-bulb A is marked “25.0 W 120. V,” and light-bulb B is marked “100. W 120. V.” These labels mean that each light-bulb has its respective power delivered to it when it is connected to a constant 120. - V source. (a) Find the resistance of each light-
> A typical cell phone consumes an average of about 1.00 W of electrical power and operates on 3.80 V. (a) What average current does the phone draw from its battery? (b) Calculate the energy stored in a fully charged battery if the phone requires charging
> A typical lightning bolt may last for 0.200 s and transfer 1.00 x 1020 electrons. Calculate the average current in the lightning bolt.
> The heating element of a coffeemaker operates at 120. V and carries a current of 2.00 A. Assuming the water absorbs all the energy converted by the resistor, calculate how long it takes to heat 0.500 kg of water from room temperature (23.0°C) to the boil
> A portable coffee heater supplies a potential difference of 12.0 V across a Nichrome heating element with a resistance of 2.00 Ω. (a) Calculate the power consumed by the heater. (b) How many minutes would it take to heat 1.00 kg of coffee from 20.0°C to
> Residential building codes typically require the use of 12 - gauge copper wire (diameter 0.205 cm) for wiring receptacles. Such circuits carry currents as large as 20.0 A. If a wire of smaller diameter (with a higher gauge number) carried that much curre
> A 1.50-kg iron horseshoe initially at 600°C is dropped into a bucket containing 20.0 kg of water at 25.0°C. What is the final temperature of the water–horseshoe system? Ignore the heat capacity of the container and assume a negligible amount of water boi
> If electrical energy costs $0.12 per kilowatt - hour, how much does it cost to (a) Burn a 100 - W light-bulb for 24 h? (b) Operate an electric oven for 5.0 h if it carries a current of 20.0 A at 220 V?
> A 5.00 - V power supply provides a maximum current of 10.0 A. (a) Calculate the maximum power delivered by the power supply. (b) How many 2.00 - W cell phone chargers could be powered by the power supply? Include fractional numbers in your answer.
> A platinum resistance thermometer has resistances of 200.0 Ω when placed in a 0°C ice bath and 253.8 Ω when immersed in a crucible containing melting potassium. What is the melting point of potassium? Hint: First determine the resistance of the platinum
> In one form of plethysmograph (a device for measuring volume), a rubber capillary tube with an inside diameter of 1.00 mm is filled with mercury at 20°C. The resistance of the mercury is measured with the aid of electrodes sealed into the ends of the tub
> An engineer needs a resistor with a zero overall temperature coefficient of resistance at 20.0°C. She designs a pair of circular cylinders, one of carbon and one of Nichrome as shown in Figure P17.32. The device must have an overall resistance
> (a) A 34.5 - m length of copper wire at 20.0°C has a radius of 0.25 mm. If a potential difference of 9.0 V is applied across the length of the wire, determine the current in the wire. (b) If the wire is heated to 30.0°C while the 9.0 - V potential differ
> A wire 3.00 m long and 0.450 mm2 in cross - sectional area has a resistance of 41.0 Ω at 20.0°C. If its resistance increases to 41.4 Ω at 29.0°C, what is the temperature coefficient of resistivity?
> In the Bohr model of the hydrogen atom, an electron in the lowest energy state moves at a speed equal to 2.19 x 106 m/s in a circular path having a radius of 5.29 x 10-11 m. What is the effective current associated with this orbiting electron?
> At 20.0°C, the carbon resistor in an electric circuit connected to a 5.0 - V battery has a resistance of 2.0 x 102 Ω. What is the current in the circuit when the temperature of the carbon rises to 80.0°C?
> At what temperature will aluminum have a resistivity that is three times the resistivity of copper at room temperature?
> An aluminum calorimeter with a mass of 0.100 kg contains 0.250 kg of water. The calorimeter and water are in thermal equilibrium at 10.0°C. Two metallic blocks are placed into the water. One is a 50.0-g piece of copper at 80.0°C. Th
> An air-filled parallel-plate capacitor with capacitance C0 stores charge Q on plates separated by distance d. The potential difference across the plates is ΔV0 and the energy stored is PEC,0. If the capacitor is disconnected from its voltage source and t
> Gold is the most ductile of all metals. For example, one gram of gold can be drawn into a wire 2.40 km long. The density of gold is 19.3 x 103 kg/m3, and its resistivity is 2.44 x 10-8 Ω · m. What is the resistance of such a wire at 20.0°C?
> A length of aluminum wire has a resistance of 30.0 Ω at 20.0°C. When the wire is warmed in an oven and reaches thermal equilibrium, the resistance of the wire increases to 46.2 Ω. (a) Neglecting thermal expansion, find the temperature of the oven. (b) Qu
> Digital thermometers often make use of thermistors, a type of resistor with resistance that varies with temperature more than standard resistors. Find the temperature coefficient of resistivity for a linear thermistor with resistances of 75.0 Ω at 0.00°C
> If a certain silver wire has a resistance of 6.00 Ω at 20.0°C, what resistance will it have at 34.0°C?
> Starting from Ohm’s law, show that E = Jρ, where E is the magnitude of the electric field (assumed constant) and J = I/A is called the current density. The result is in fact true in general.
> The human body can exhibit a wide range of resistances to current depending on the path of the current, contact area, and sweatiness of the skin. Suppose the resistance across the chest from the left hand to the right hand is 1.0 x 106 Ω. (a) How much vo
> The resistivity of copper is 1.70 x 10-8 Ω · m. (a) Find the resistance of a copper wire with a radius of 1.29 mm and a length of 1.00 m. (b) Calculate the volume of copper in the wire. (c) Suppose that volume of copper is formed into a new wire with a l
> A rectangular block of copper has sides of length 10. cm, 20. cm, and 40. cm. If the block is connected to a 6.0 - V source across two of its opposite faces, what are (a) The maximum current and (b) The minimum current the block can carry?
> A copper wire has a circular cross section with a radius of 1.25 mm. (a) If the wire carries a current of 3.70 A, find the drift speed of electrons in the wire. (Take the density of mobile charge carriers in copper to be n = 1.10 x 1029 electrons/m3.) (b
> A wire 50.0 m long and 2.00 mm in diameter is connected to a source with a potential difference of 9.11 V, and the current is found to be 36.0 A. Assume a temperature of 20°C and, using Table 17.1, identify the metal out of which the wire is m
> A large room in a house holds 975 kg of dry air at 30.0°C. A woman opens a window briefly and a cool breeze brings in an additional 50.0 kg of dry air at 18.0°C. At what temperature will the two air masses come into thermal equilibrium, assuming they for
> The current supplied by a battery in a portable device is typically 0.15 A. Find the number of electrons passing through the device in one hour.
> A potential difference of 12 V is found to produce a current of 0.40 A in a 3.2 - m length of wire with a uniform radius of 0.40 cm. What is (a) The resistance of the wire? (b) The resistivity of the wire?
> A wire of diameter 0.800 mm and length 25.0 m has a measured resistance of 1.60 Ω. What is the resistivity of the wire?
> Nichrome wire of cross - sectional radius 0.791 mm is to be used in winding a heating coil. If the coil must carry a current of 9.25 A when a voltage of 1.20 x 102 V is applied across its ends, find (a) The required resistance of the coil and (b) The len
> Suppose you wish to fabricate a uniform wire out of 1.00 g of copper. If the wire is to have a resistance R = 0.500 Ω, and if all the copper is to be used, what will be (a) The length and (b) The diameter of the wire?
> A person notices a mild shock if the current along a path through the thumb and index finger exceeds 80. μA. Compare the maximum possible voltage without shock across the thumb and index finger with a dry - skin resistance of 4.0 x 105 Ω and a wet - skin
> Germanium is a semiconducting metal with a resistivity of 0.460 Ω · m. (a) Determine the current per unit area through a 5.00 - V germanium junction with a length of 2.00 mm. (b) Find the current through the junction if its cross - sectional area is 2.00
> A voltmeter connected across the terminals of a tungsten - filament light bulb measures 115 V when an ammeter in line with the bulb registers a current of 0.522 A. (a) Find the resistance of the light bulb. (b) Find the resistivity of tungsten at the bul
> An electric heater carries a current of 13.5 A when operating at a voltage of 1.20 x 102 V. What is the resistance of the heater?
> If a current of 80.0 mA exists in a metal wire, (a) How many electrons flow past a given cross section of the wire in 10.0 min? (b) In what direction do the electrons travel with respect to the current?
> A medium-sized banana provides about 105 Calories of energy. (a) Convert 105 Cal to joules. (b) Suppose that amount of energy is transformed into kinetic energy of a 1.00-kg object initially at rest. Calculate the final speed of the object. (c) If that s
> An ionized oxygen molecule (O2+) at point A has charge +e and moves at 2.00 x 103 m/s in the positive x - direction. A constant electric force in the negative x - direction slows the molecule to a stop at point B, a distance of 0.750 mm past A on the x -
> (a) Find the potential difference ΔVe required to stop an electron (called a “stopping potential”) moving with an initial speed of 2.85 x 107 m/s. (b) Would a proton traveling at the same speed require a greater or lesser magnitude potential difference?
> An electron is fired at a speed v0 = 5.6 x 106 m/s and at an angle θ0 = -45° between two parallel conducting plates that are D = 2.0 mm apart, as in Figure P16.72. If the voltage difference between the plates is ΔV = 1
> Metal sphere A of radius 12.0 cm carries 6.00 μC of charge, and metal sphere B of radius 18.0 cm carries -4.00 μC of charge. If the two spheres are attached by a very long conducting thread, what is the final distribution of charge on the two spheres?
> Two positive charges each of charge q are fixed on the y - axis, one at y = d and the other at y = -d as in Figure P16.70. A third positive charge 2q located on the x - axis at x = 2d is released from rest. Find symbolic expressions for (a) The total ele
