QuestionĪ hairdryer transfers 48,000 J of energy in one minute. Since twice as much energy is transferred by motor one each second, it is possible to say that motor one is twice as powerful as motor two. The equation used to calculate the power is: So the more powerful a device is, the more energy it will transfer each second. The rate at which this energy is transferred is called power. What is the power of the motor? Your answer should include: 55W / 55 What is the efficiency of a 60W lightbulb that produces 3W of light? 0.When work is done on an object, energy is transferred. A An electric motor uses 275J to lift a load in 5s. Formula to calculate efficiency: Efficiency Physics Formula. B A or B? Which of these devices uses the most energy? A - a 1kW iron used for 1 hours. In other words, efficiency is the ratio of energy output by energy input. A or B? Which of these devices uses the most energy? A - a 2kW heater used for 4 hours. So, although the energy efficient bulb has a higher initial cost, it will save money in the long term. Because the filament bulb is less efficient, the cost of electricity for the filament bulb will be much higher than the energy saving bulb. However, the energy saving bulb has a much longer lifetime than the filament bulb, which will need to be replaced regularly.
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This means that, for the same amount of electrical energy, the energy saving bulb will produce more light than the filament bulb.Įnergy saving bulbs are usually more expensive to buy compared to filament bulbs. As a lot of heat is also produced, filament bulbs are not very efficient.Įnergy saving light bulbs do not use this method and are more efficient.
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The filament gets hot and glows, producing light. Traditional, filament light bulbs use electricity flowing through a thin piece of wire called a filament.
#POWER FORMULA PHYSICS CALCULATOR PORTABLE#
Efficiency = useful energy out ÷ total energy inĪ portable speaker coverts 150J of electrical energy into 30J of sound energy.Only 400J of kinetic energy was generated by the drill. When doing a calculation your working and answer should use the same. If you get answer that is bigger than 1 or 100%, you have made a mistake somewhere in your calculation!Ī power drill uses 500J of electricity. The calculator display shows the power of ten as two separate digits on the right. For example, an efficiency of 0.25 is the same as an efficiency of 25%.īecause some energy is always wasted from every device, efficiency should always be less than 1 or less than 100%. It can be written as a number between 0 and 1 or as a %. Or Efficiency = useful power out ÷ total power in You need to remember the equations for efficiency: Efficiency = useful energy out ÷ total energy in A car engine is designed to produce kinetic energy but also produces heat and sound which is dissipated into the surroundings.Įfficiency is a measurement of how much energy is converted usefully (compared to how much is wasted).For example, a light bulb is designed to produce light, but also produces heat energy which is dissipated into the surroundings.
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Therefore, the efficiency is 10÷60=0.17 (or 17%) EfficiencyĪll devices waste some energy, usually as heat due to friction between moving parts. They can be used to calculate efficiency.įor this Sankey diagram, the useful energy output is 10J and the total energy input is 60J. Sankey diagrams were introduced in a previous lesson.