The amount of electrical energy transferred to an appliance depends on its power and the length of time it is switched on. Charles Howard Candler Professor of Physics Emeritus, Emory University, Atlanta. An object that has motion - whether it is vertical or horizontal motion - has kinetic energy. https://www.britannica.com/science/E-mc2-equation, American Museum of Natural History - E=mc2, Public Broadcasting Corporation - NOVA - The Legacy of E = mc2. in maintaining the current in an electric circuit for a given time: E = mc 2, equation in German-born physicist Albert Einstein’s theory of special relativity that expresses the fact that mass and energy are the same physical entity and can be changed into each other. The equation … Energy density is the computation of the amount of energy that can be stored in a given mass of a substance or a system. Then click the button to view the answers. 4. 1. Copyright © | Privacy Statement | Cookie Policy, E is the energy transferred in kilowatt-hours, kWh. This equation reveals that the kinetic energy of an object is directly proportional to the square of its speed. The formula that links energy and power is: The unit of energy is the joule, the unit of power is the watt, and the unit of time is the second. Kinetic energy is the energy of motion. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. By using this website, you agree to our use of cookies. Important equations regarding electric energy are explained here, The amount of electrical that is consumed by an electrical energy can be easily calculated and the cost of electrical energy used for a particular appliance can also be calculated. Electrical energy calculations. The kinetic energy is dependent upon the square of the speed. One unit is 1 kWh. Thus, each body of rest mass m possesses mc2 of “rest energy,” which potentially is available for conversion to other forms of energy. Omissions? If an object is moving, then it possesses kinetic energy. To keep matters simple, we will focus upon translational kinetic energy. The amount of mains electrical energy transferred is measured in kilowatt-hours, kWh. For starters, the E stands for energy and the m stands for mass, a measurement of the quantity of matter. The mass-energy relation, moreover, implies that, if energy is released from the body as a result of such a conversion, then the rest mass of the body will decrease. - Fire2Fusion All rights reserved. where m = mass of object. Efficiency Formula Questions: 1) A construction worker puts 20 J of energy in to one strike of his hammer on the head of a nail. The amount of mains electrical energy transferred is measured in kilowatt-hours, kWh. The cost of consumption of electric energy in a house = no. Distributing and simplifying the equation gives you the equation for work in terms of the spring constant and position: The work done on the spring changes the potential energy stored in the spring. Furthermore, the energy of a body at rest could be assigned an arbitrary value. Thus, the new KE is (320 000 J)/4 or 80 000 J. In special relativity, however, the energy of a body at rest is determined to be mc2. η = 40% Kinetic energy is a scalar quantity; it does not have a direction. In physical theories prior to that of special relativity, mass and energy were viewed as distinct entities. One unit is 1 kWh. The amount of kinetic energy that it possesses depends on how much mass is moving and how fast the mass is moving. The electric energy is defined as the total work done or energy supplied by the source of e.m.f. To know more about equations of electric energy visit us. Estimate its new kinetic energy if it is moving at 30 mi/hr. The following equation is used to represent the kinetic energy (KE) of an object. A 900-kg compact car moving at 60 mi/hr has approximately 320 000 Joules of kinetic energy. Answer: The efficiency can be found using the formula: η = 0.40 x 100%. If the speed is reduced by a factor of 2 (as in from 60 mi/hr to 30 mi/hr) then the KE will be reduced by a factor of 4.               Electric energy = electric power × time = P × t. Thus the formula for electric energy is given by: Electric energy = P × t = V × I × t = I2 × R × t = V2t / R. Copyright © 2018.