Energy and Power - ENGR 10 (P. Hsu 2007)
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Vocabulary flashcards covering key concepts, terms, and formulas from the energy and power notes (P. Hsu 2007).
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39 Terms
Energy
A fundamental entity of nature that is transferred between parts of a system in the production of physical change and usually regarded as the capacity for doing work.
Kinetic Energy
Energy of motion; KE = 1/2 m v^2.
Potential Energy
Energy stored by position; energy due to height or other fields; PE = m g h.
Mechanical Energy
The sum of kinetic and potential energy in a system.
Chemical Energy
Energy stored in chemical bonds; released or absorbed during chemical reactions.
Gravitational Potential Energy
Potential energy due to height in a gravitational field; a form of PE.
Electrical Energy
Energy associated with the position or movement of electric charges.
Thermal Energy
Internal energy related to temperature; commonly observed as heat.
Nuclear Energy
Energy stored in atomic nuclei; released in nuclear reactions.
Elastic Energy
Potential energy stored in a deformed elastic object (compression/stretching).
Radiant Energy
Energy carried by electromagnetic radiation (light).
Sound Energy
Energy carried by sound waves.
Work
Transfer of energy when a force acts over a distance; W = F d; energy transformed, not created.
Power
Rate at which energy is transformed; Power = energy / time; unit is the Watt (W).
Efficiency
Ratio of useful output energy to input energy; Efficiency = Useful Output / Input.
Conservation of Energy
Energy is never created or destroyed; it only changes form; total energy remains constant.
Energy Transformation
Process of changing energy from one form to another (e.g., chemical to kinetic).
Energy Input
Energy supplied to a system.
Energy Output
Useful energy delivered by a system.
PE = m g h
Equation for gravitational potential energy: PE = m g h.
KE = 1/2 m v^2
Equation for kinetic energy: KE = 1/2 m v^2.
1 J (Joule)
Unit of energy; equal to 1 N·m.
1 W (Watt)
Unit of power; equal to 1 J/s.
Kilowatt-hour (kWh)
Unit of energy; 1 kWh = 3.6 × 10^6 J.
BTU (British Thermal Unit)
Energy unit ≈ 1055 J.
Calorie (cal)
Energy required to raise 1 g of water by 1°C; 4.184 J.
Food Calorie (kcal)
Energy in food; 1 kcal = 4184 J.
Flow rate (gps)
Gallons per second; a measure of how fast water flows.
Horsepower (HP)
Unit of power; 1 HP ≈ 746 W.
Gasoline Energy Content
About 1.3 × 10^8 J per gallon of gasoline.
Coal Energy Content
About 1.6 × 10^7 J per pound of coal.
Candy Bar Energy Content
About 2 × 10^5 J per candy bar.
AA Battery Energy
About 10^3 J (rough estimate from the notes).
Energy Transformation Machine
Devices that convert energy from one form to another (e.g., engines, turbines).
Brake Energy Transformation
Kinetic energy of a moving car is converted to heat in brakes.
Power vs. Energy Concept
Energy is a total amount; power is the rate of energy transformation (energy per unit time).
P = F × v
Power equals force times velocity; used in bike cycling example.
1 gps
1 gallon per second; a measure used in flow rate analogy.
Wind Turbine Energy Transformation
A wind turbine converts kinetic energy of wind into mechanical and electrical energy.