Domanda del libro di testo
A 2800-W oven is connected to a 240-V source. How long will it take to bring 150 mL of 15°C water to 100°C assuming 65% efficiency?
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Ch. 25 - Electric Current and Resistance
Giancoli Douglas5th editionPhysics for Scientists and EngineersISBN: 9780137488179
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TOC.tableOfContents
- Ch. 01 - Introduction, Measurement, Estimating10
- Ch. 02 - Describing Motion: Kinematics in One Dimension30
- Ch. 03 - Kinematics in Two or Three Dimensions; Vectors15
- Ch. 04 - Dynamics: Newton's Laws of Motion16
- Ch. 05 - Using Newton's Laws: Friction, Circular Motion, Drag Forces22
- Ch. 06 - Gravitation and Newton's Synthesis10
- Ch. 07 - Work and Energy21
- Ch. 08 - Conservation of Energy33
- Ch. 09 - Linear Momentum26
- Ch. 10 - Rotational Motion41
- Ch. 11 - Angular Momentum; General Rotation27
- Ch. 12 - Static Equilibrium; Elasticity and Fracture27
- Ch. 13 - Fluids28
- Ch. 14 - Oscillations14
- Ch. 15 - Wave Motion35
- Ch. 16 - Sound5
- Ch. 17 - Temperature, Thermal Expansion, and the Ideal Gas Law40
- Ch. 18 - Kinetic Theory of Gases18
- Ch. 19 - Heat and the First Law of Thermodynamics31
- Ch. 20 - Second Law of Thermodynamics32
- Ch. 21 - Electric Charge and Electric Field7
- Ch. 23 - Electric Potential20
- Ch. 24 - Capacitance, Dielectrics, Electric Energy, Storage15
- Ch. 25 - Electric Current and Resistance32
- Ch. 26 - DC Circuits22
- Ch. 27 - Magnetism21
- Ch. 28 - Sources of Magnetic Field24
- Ch. 29 - Electromagnetic Induction and Faraday's Law21
- Ch. 30 - Inductance, Electromagnetic Oscillations, and AC Circuits42
- Ch. 31 - Maxwell's Equations and Electromagnetic Waves25
- Ch. 32 - Light: Reflection and Refraction42
- Ch. 33 - Lenses and Optical Instruments21
- Ch. 34 - The Wave Nature of Light: Interference and Polarization26
- Ch. 35 - Diffraction24
- Ch. 36 - The Special Theory of Relativity29
- Ch. 38 - Quantum Mechanics1
- Ch. 40 - Molecules and Solids6
- Ch. 43 - Elementary Particles3
- Ch. 44 - Astrophysics and Cosmology9
Giancoli Douglas5th editionPhysics for Scientists and EngineersISBN: 9780137488179Non è quello che usi tu?Cambia libro di testo
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Giancoli Douglas 5th editionCh. 25 - Electric Current and ResistanceProblema 82
Giancoli Douglas 5th editionCh. 25 - Electric Current and ResistanceProblema 82Capitolo 24, Problema 82
A 100-W, 120-V incandescent lightbulb has a resistance of 12 Ω when cold (20°C) and 150 Ω when on (hot). Calculate its power consumption (a) at the instant it is turned on, and (b) after a few moments when it is hot.
Guida verificata passo dopo passo1
Step 1: Understand the problem. The power consumption of the lightbulb depends on its resistance and the voltage applied. When the bulb is cold, its resistance is 12 Ω, and when it is hot, its resistance is 150 Ω. Use the formula for power: P = V² / R, where P is power, V is voltage, and R is resistance.
Step 2: For part (a), calculate the power consumption at the instant the bulb is turned on (cold resistance). Substitute the given values into the formula: P = (120²) / 12. Simplify the expression to find the power when the bulb is cold.
Step 3: For part (b), calculate the power consumption after the bulb has been on for a while (hot resistance). Substitute the given values into the formula: P = (120²) / 150. Simplify the expression to find the power when the bulb is hot.
Step 4: Compare the results from part (a) and part (b). Notice that the power consumption is higher when the bulb is cold because the resistance is lower, and it decreases as the bulb heats up and its resistance increases.
Step 5: Reflect on the physical meaning. The change in resistance is due to the temperature dependence of the filament material. As the filament heats up, its resistance increases, which reduces the current and power consumption over time.
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Ohm's Law
Ohm's Law states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. It is mathematically expressed as V = I * R. This principle is essential for calculating the current in the lightbulb when it is turned on and when it is hot.
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Percorso guidato
03:07
Resistance and Ohm's Law
Power in Electrical Circuits
The power (P) consumed by an electrical device is defined as the product of the voltage (V) across it and the current (I) flowing through it, expressed as P = V * I. This concept is crucial for determining the power consumption of the lightbulb at both cold and hot states, as it allows us to calculate how much energy is being used.
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Percorso guidato
06:18Power in Circuits
Temperature Dependence of Resistance
The resistance of materials, particularly metals, typically increases with temperature. In the case of the incandescent lightbulb, its cold resistance is 12 Ω at 20°C, but it rises to 150 Ω when the bulb is hot. Understanding this temperature dependence is vital for accurately calculating the power consumption at the moment it is turned on versus after it has warmed up.
Video consigliato:
Percorso guidato
04:54Introduction To Temperature Scales
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