Physics for Scientists and Engineers with Modern Physics
4th Edition
ISBN: 9780131495081
Author: Douglas C. Giancoli
Publisher: Addison-Wesley
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Textbook Question
Chapter 25, Problem 78GP
An electric heater is used to heat a room of volume 54 m3. Air is brought into the room at 5°C 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 20° C, what minimum wattage must the heater have? (The specific heat of air is about 0.17 kcal/kg·C°.)
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Chapter 25 Solutions
Physics for Scientists and Engineers with Modern Physics
Ch. 25.2 - If 1 million electrons per second pass a point in...Ch. 25.3 - Prob. 1BECh. 25.4 - Return to the Chapter-Opening Question, page 651,...Ch. 25.4 - Prob. 1DECh. 25.4 - Prob. 1EECh. 25.4 - Prob. 1FECh. 25.6 - How many 60-W 120-V lightbulbs can operate on a...Ch. 25.7 - Each channel of a stereo receiver is capable of an...Ch. 25 - What quantity is measured by a battery rating...Ch. 25 - When an electric cell is connected to a circuit,...
Ch. 25 - When a flashlight is operated, what is being used...Ch. 25 - One terminal of a car battery is said to be...Ch. 25 - When you turn on a water faucet, the water usually...Ch. 25 - Can a copper wire and an aluminum wire of the same...Ch. 25 - The equation P = V2/R indicates that the power...Ch. 25 - What happens when a lightbulb burns out?Ch. 25 - If the resistance of a small immersion heater (to...Ch. 25 - Prob. 10QCh. 25 - Explain why lightbulbs almost always burn out just...Ch. 25 - Which draws more current, a 100-W lightbulb or a...Ch. 25 - Electric power is transferred over large distances...Ch. 25 - A 15-A fuse blows repeatedly. Why is it dangerous...Ch. 25 - When electric lights are operated on low-frequency...Ch. 25 - Driven by ac power, the same electrons pass back...Ch. 25 - The heating element in a toaster is made of...Ch. 25 - Is current used up in a resistor? Explain.Ch. 25 - Compare the drift velocities and electric currents...Ch. 25 - A voltage V is connected across a wire of length l...Ch. 25 - Why is it more dangerous to turn on an electric...Ch. 25 - ( A current of 1.30 A flows in a wire. How many...Ch. 25 - (I) A service station charges a battery using a...Ch. 25 - (I) What is the current in amperes if 1200 Na+...Ch. 25 - (I) What is the resistance of a toaster if 120V...Ch. 25 - (II) An electric clothes dryer has a heating...Ch. 25 - (II) A hair dryer draws 9.5 A when plugged into a...Ch. 25 - (II) A 4.5-V battery is connected to a bulb whose...Ch. 25 - (II) A bird stands on a dc electric transmission...Ch. 25 - (II) A 12-V battery causes a current of 0.60 A...Ch. 25 - (II) An electric device draws 6.50 A at 240 V. (a)...Ch. 25 - (I) What is the diameter of a 1.00-m length of...Ch. 25 - (I) What is the resistance of a 4.5-m length of...Ch. 25 - (II) Calculate the ratio of the resistance of 10.0...Ch. 25 - (II) Can a 2.2-mm-diameter copper wire have the...Ch. 25 - (II) A sequence of potential differences V is...Ch. 25 - (II) How much would you have 10 raise the...Ch. 25 - (II) A certain copper wire has a resistance of...Ch. 25 - (II) Determine at what temperature aluminum will...Ch. 25 - (II) A 100-W lightbulb has a resistance of about...Ch. 25 - (II) Compute the voltage drop along a 26-m length...Ch. 25 - (II) Two aluminum wires have the same resistance....Ch. 25 - (II) A rectangular solid made of carbon has sides...Ch. 25 - (II) A length of aluminum wire is connected to a...Ch. 25 - (II) Small changes in the length of an object can...Ch. 25 - (II) A length of wire is cut in half and the two...Ch. 25 - (III) For some applications, it is important that...Ch. 25 - (III) Determine a formula for the total resistance...Ch. 25 - (III) The filament of a lightbulb has a resistance...Ch. 25 - (III) A 10.0-m length of wire consists of 5.0 m of...Ch. 25 - (III) A hollow cylindrical resistor with inner...Ch. 25 - (I) What is the maximum power consumption of a...Ch. 25 - (I) The heating element of an electric oven is...Ch. 25 - (I) What is the maximum voltage that can be...Ch. 25 - (I) (a) Determine the resistance of, and current...Ch. 25 - (II) An electric power plant can produce...Ch. 25 - (II) A 120-V hair dryer has two settings: 850 W...Ch. 25 - (II) A 115-V fish-tank heater is rated at 95W....Ch. 25 - (II) You buy a 75-W lightbulb in Europe, where...Ch. 25 - (II) How many kWh of energy does a 550-W toaster...Ch. 25 - (II) At 0.095/kWh, what does it cost to leave a...Ch. 25 - (II) What is the total amount of energy stored in...Ch. 25 - (II) An ordinary flashlight uses two D-cell 1.5-V...Ch. 25 - (II) How many 75-W lightbulbs, connected to 120V...Ch. 25 - (II) An extension cord made of two wires of...Ch. 25 - (II) A power station delivers 750kW of power at...Ch. 25 - (III) A small immersion heater can be used in a...Ch. 25 - (III) The current in an electromagnet connected to...Ch. 25 - (III) A 1.0-m-long round tungsten wire is to reach...Ch. 25 - (I) Calculate the peak current in a 2.7-k resistor...Ch. 25 - (I) An ac voltage, whose peak value is 180 V, is...Ch. 25 - (II) Estimate the resistance of the 120-Vrms...Ch. 25 - (II) The peak value of an alternating current in a...Ch. 25 - (II) An 1800-W are welder is connected to a...Ch. 25 - (II) (a) What is the maximum instantaneous power...Ch. 25 - (II) A heater coil connected to a 240-Vrrms ac...Ch. 25 - (II) For a time-dependent voltage V(t), which is...Ch. 25 - Prob. 57PCh. 25 - (II) A 5.80-m length of 2.0-mm-diameter wire...Ch. 25 - (II) At a point high in the Earths atmosphere....Ch. 25 - (I) What is the magnitude of the electric field...Ch. 25 - (II) A neuron is stimulated with an electric...Ch. 25 - (III) During an action potential, Na+ ions move...Ch. 25 - A person accidentally leaves a car with the lights...Ch. 25 - How many coulombs are there in 1.00 ampere-hour?Ch. 25 - You want to design a portable electric blanket...Ch. 25 - What is the average current drawn by a 1.0-hp...Ch. 25 - Prob. 67GPCh. 25 - The heating element of a 110-V, 1500-W heater is...Ch. 25 - (a) A particular household uses a 1.8-kW healer...Ch. 25 - A small city requires about 15 MW of power....Ch. 25 - A 1400-W hair dryer is designed for 117 V. (a)...Ch. 25 - The wiring in a house must be thick enough so it...Ch. 25 - Prob. 73GPCh. 25 - Suppose a current is given by the equation I =...Ch. 25 - A microwave oven running at 65% efficiency...Ch. 25 - Prob. 76GPCh. 25 - 220 V is applied to two different conductors made...Ch. 25 - An electric heater is used to heat a room of...Ch. 25 - A 2800-W oven is connected to a 240-V source, (a)...Ch. 25 - A proposed electric vehicle makes use of storage...Ch. 25 - A 12.5- resistor is made from a coil of copper...Ch. 25 - A fish-tank heater is rated at 95 W when connected...Ch. 25 - A 100-W, 120-V lightbulb has a resistance of 12 ...Ch. 25 - In an automobile, the system voltage varies from...Ch. 25 - The Tevatron accelerator at Fermilab (Illinois) is...Ch. 25 - Lightbulb A is rated at 120 V and 40 W for...Ch. 25 - An air conditioner draws 14 A at 220-V ac. The...Ch. 25 - Copper wire of diameter 0.259 cm is used to...Ch. 25 - Battery-powered electricity is very expensive...Ch. 25 - How far does an average electron move along the...Ch. 25 - A copper pipe has an inside diameter of 3.00 cm...Ch. 25 - For the wire in Fig. 2539, whose diameter varies...Ch. 25 - The cross section of a portion of wire increases...Ch. 25 - Prob. 94GPCh. 25 - The level of liquid helium (temperature 4 K) in...Ch. 25 - (II) The resistance, R, of a particular thermistor...
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