CLASS 7 · LEARNING KNOWLEDGE
Power and Efficiency – Basic Principles
How it works
Power is the measure of how much work or energy is converted in a certain amount of time. It is measured in watts (W). The formula is: Power = work / time. Efficiency describes how much of the supplied energy is converted into usable energy. It is the ratio of output to input energy and is usually given as a percentage. An efficiency of less than 100 % means that part of the energy is converted into other, usually undesired forms of energy, such as heat.
Note
Power is calculated as work divided by time. Efficiency results from the quotient of usable and supplied energy, usually as a percentage.
Power is calculated as work divided by time. Efficiency results from the quotient of usable and supplied energy, usually as a percentage.
An example
A machine does 2000 joules of work in 10 seconds. How much power does it have?
Power is calculated as work divided by time: 2000 J / 10 s = 200 W. The machine has a power of 200 watts.
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50 Exercises
To the learning unit →Own explanation and own practice exercises by AmyMath. Subject reference framework: Physics. The topic assignment may vary by federal state.