What is efficiency ?

What is efficiency ?

coefficient of performance (COP) - a term that can be applied, perhaps to every system and device.Even a person has the efficiency, however, probably does not yet exist an objective formula for its location.This article will tell in detail what is efficiency and how it can be calculated for different systems.


efficiency - a measure of the efficiency of a system in relation to the impact or energy conversion.Efficiency - immense value and a numeric value is represented in the range of 0 to 1, or as a percentage.

general formula

efficiency denoted Ƞ.

general mathematical formula for finding efficiency is written as follows:

Ƞ = A / the Q, where A - useful energy / work carried out by the system, and the Q - energy consumed by the system for the organization of the process of obtaining useful output.

Efficiency, unfortunately, is always less than or equal to the unit, since, according to the law of conservation of energy, we can not get the work more than the energy spent.Furthermore, the efficiency, in fact, rarely equals unity, as the useful work is always accompanied by the presence of loss, for example, heating mechanism.

efficiency heat engine

heat engine - a device which converts thermal energy into mechanical energy.The heat engine operation is determined by the difference between the amount of heat produced by the heater, and the amount of heat given cooler, so the efficiency is determined by the formula:

  • Ƞ = Qn-qx / Qn, where Qn - the amount of heat received from the heater, and qx- the amount of heat given to the cooler.

believed that provide the highest efficiency of engines running on the Carnot cycle.In this case, the efficiency is determined by the formula:

  • Ƞ = T1-T2 / T1, where T1 - the temperature of a hot spring, T2 - temperature of the cold source.

efficiency electric motor

electric motor - a device that converts electrical energy into mechanical energy, so that the efficiency in this case - is the coefficient of efficiency of the device in relation to conversion of electrical energy into mechanical energy.The formula of finding the efficiency of the electric motor is as follows:

  • Ƞ = P2 / P1, where P1 - applying an electric power, P2 - a useful mechanical power, worked out motor.

Electrical power is the product of current and voltage of the system (P = UI), and a mechanical - as the ratio of work per unit time (P = A / t)

efficiency transformer

transformer - a device that converts alternating current of onevoltage into another alternating current voltage, while retaining frequency.In addition, the transformers can also convert AC power to DC.

transformer Efficiency is the formula:

  • Ƞ = 1/1 + (P0 + PL * n2) / (P2 * n), where P0 - loss idling, PL - load losses, P2 - active power, given to the load, n - the relative degree of loading.

efficiency or efficiency?

It is worth noting that in addition to efficiency, there are a number of indicators that characterize the efficiency of energy processes, and sometimes we can find the description of the type - the efficiency of about 130%, but in this case it should be understood that the term used is not entirely correct, and it is likelyauthor or manufacturer understands by this abbreviation slightly different characteristics.

For example, heat pumps differ in that they can give more heat than spend.Thus, the chiller may withdraw from the cooled object more heat than the spent energy equivalent to the removal of the organization.Indicator chiller efficiency is called coefficient of performance, denoted by the letter and ɛ is determined by the formula: Ɛ = Qx / A, where Qx - heat rejected from the cold end, A - work expended on the removal process.However, sometimes called the coefficient of performance and efficiency of the chiller.

It is also interesting that the efficiency of boilers using fossil fuel, is calculated generally on a lower calorific value, thus it can get more than one.Nevertheless, it is still traditionally referred efficiency.Boiler efficiency can be determined by a higher calorific value, and then it will always be less than unity, but in this case is inconvenient to compare these parameters with other boiler installations.

Read also the article The laws of thermodynamics.