PHYSICAL QUANTITY

Efficiency: formulas and units of measurement

Efficiency: symbol η, unit %. Formulas and explanations for Mechanics, MCT and thermodynamics.

\eta

\%

percentage

KEY CONNECTIONS

Formulas

η = \frac{A _{useful}}{A _{input}}

η = Apol / Azatr

η = \frac{Q _{useful}}{Q _{input}}

η = Qpol / Qzatr

η = \frac{Q _{1} - Q _{2}}{Q _{1}}

η = (Q₁ − Q₂) / Q₁

η = \frac{T _{1} - T _{2}}{T _{1}}

η = (T₁ − T₂) / T₁

NOTATION

$\eta$: Efficiency is the proportion of useful energy used.
$A_{\text{useful}}$: Useful work is the part of the work expended that is used for its intended purpose.
$A_{\text{input}}$: Work expended is all the work done by a system or mechanism.
$Q_{\text{useful}}$: Useful heat is the part of the received heat used for its intended purpose.
$Q_{\text{input}}$: Wasted heat is the entire amount of heat transferred to the system.
$Q_1$: Heater heat is the energy received by the working fluid from the heater.
$Q_2$: The heat of the refrigerator is the energy given by the working fluid to the refrigerator.
$T_1$: Heater temperature is the temperature of the hotter heat source.
$T_2$: Refrigerator temperature is the temperature of a cooler heat source.

THEORY

PRACTICE