Textbook Question
What is the value of resistor R in FIGURE EX28.16?
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Ch 28: Fundamentals of Circuits
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796
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Table of contents
- Ch 01: Concepts of Motion35
- Ch 02: Kinematics in One Dimension75
- Ch 03: Vectors and Coordinate Systems58
- Ch 04: Kinematics in Two Dimensions60
- Ch 05: Force and Motion23
- Ch 06: Dynamics I: Motion Along a Line53
- Ch 07: Newton's Third Law27
- Ch 08: Dynamics II: Motion in a Plane52
- Ch 09: Work and Kinetic Energy56
- Ch 10: Interactions and Potential Energy50
- Ch 11: Impulse and Momentum56
- Ch 12: Rotation of a Rigid Body71
- Ch 13: Newton's Theory of Gravity52
- Ch 14: Fluids and Elasticity44
- Ch 15: Oscillations55
- Ch 16: Traveling Waves37
- Ch 17: Superposition39
- Ch 18: A Macroscopic Description of Matter53
- Ch 19: Work, Heat, and the First Law of Thermodynamics60
- Ch 20: The Micro/Macro Connection53
- Ch 21: Heat Engines and Refrigerators34
- Ch 22: Electric Charges and Forces40
- Ch 23: The Electric Field39
- Ch 24: Gauss' Law32
- Ch 25: The Electric Potential63
- Ch 26: Potential and Field57
- Ch 27: Current and Resistance42
- Ch 28: Fundamentals of Circuits39
- Ch 29: The Magnetic Field47
- Ch 30: Electromagnetic Induction60
- Ch 31: Electromagnetic Fields and Waves32
- Ch 32: AC Circuits63
- Ch 33: Wave Optics32
- Ch 34: Ray Optics57
- Ch 35: Optical Instruments30
- Ch 36: Special Relativity38
- Ch 37: The Foundations of Modern Physics25
- Ch 38: Quantization49
- Ch 39: Wave Functions and Uncertainty31
- Ch 40: One-Dimensional Quantum Mechanics35
- Ch 41: Atomic Physics18
- Ch 42: Nuclear Physics27
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 28, Problem 14a
A typical American family uses 1000 kWh of electricity a month. What is the average current in the 120 V power line to the house?
Verified step by step guidance1
Step 1: Begin by recalling the formula for electrical power, which is \( P = IV \), where \( P \) is power in watts, \( I \) is current in amperes, and \( V \) is voltage in volts.
Step 2: Convert the monthly energy usage from kilowatt-hours (kWh) to watts. Since 1 kWh = 1000 watt-hours, multiply the given energy usage (1000 kWh) by 1000 to get the energy in watt-hours.
Step 3: Divide the total energy in watt-hours by the number of hours in a month to find the average power. Assume a month has approximately 30 days, so there are \( 30 \times 24 = 720 \) hours in a month.
Step 4: Rearrange the power formula \( P = IV \) to solve for current \( I \). This gives \( I = \frac{P}{V} \). Substitute the average power calculated in Step 3 and the given voltage (120 V) into this formula.
Step 5: Perform the division to find the average current \( I \). The result will be in amperes (A), which represents the average current flowing through the power line to the house.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Electric Power
Electric power is the rate at which electrical energy is transferred by an electric circuit. It is measured in watts (W), where 1 watt equals 1 joule per second. The power consumed by a device can be calculated using the formula P = VI, where P is power, V is voltage, and I is current. Understanding this relationship is crucial for solving problems related to electricity consumption.
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06:00
Power
Current
Current is the flow of electric charge in a circuit, measured in amperes (A). It represents the amount of charge passing through a point in the circuit per unit time. The average current can be calculated by rearranging the power formula to I = P/V, where I is current, P is power, and V is voltage. This concept is essential for determining how much current flows in a circuit based on power usage and voltage.
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05:38Intro to Current
Voltage
Voltage, or electric potential difference, is the measure of electric potential energy per unit charge between two points in a circuit. It is measured in volts (V) and indicates how much energy is available to move charges through a circuit. In this context, the standard voltage of 120 V is used to calculate the current based on the total power consumption of the household.
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Related Practice
Textbook Question
Many electric companies use time-of-day pricing in which electricity costs more during hours of high demand. Suppose electricity costs \(0.21/kWh from 10 a.m. to 6 p.m.; \)0.09/kWh at all other times. What is the annual cost of electricity for a 2.5 kW industrial pump that runs 24 hours a day?
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Textbook Question
The five identical bulbs in FIGURE EX28.11 are all glowing. The battery is ideal. What is the order of brightness of the bulbs, from brightest to dimmest? Some may be equal.
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Textbook Question
A 60 W lightbulb and a 100 W lightbulb are placed in the circuit shown in FIGURE EX28.9. Both bulbs are glowing. Which bulb is brighter? Or are they equally bright?
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Textbook Question
A typical American family uses 1000 kWh of electricity a month. On average, what is the resistance of a household?
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Textbook Question
A 100 W (120 V) incandescent lightbulb contains a 7.0-cm-long tungsten filament. The high-temperature resistivity of tungsten is 9.0 x 10⁻⁷ Ωm. What is the diameter of the filament?
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