The Energy Equation The first law of thermodynamics defines the internal energy by stating that the change in internal energy for a closed system, ΔU, is equal to the heat supplied to the system, , minus the work done by the system, : (1)

The quantitative relationship between heat transfer and temperature change contains all three factors: Q = mcΔT, where Q is the symbol for heat transfer, m is the mass of the substance, and ΔT is the change in temperature. The symbol c stands for specific heat and depends on the material and phase.

What is the formula for specific heat? The formula for specific heat capacity, C , of a substance with mass m , is C = Q /(m ⨉ ΔT) .

The equation for calculating heat energy is q=mCpΔT, where q is the heat variable, m is the mass of the object, Cp is the specific heat constant and ΔT is the temperature change.

The energy equation is an expression of the first law of thermodynamics or the law of conservation of energy. First, a balance equation for the rate of change of kinetic energy and internal energy is written. The internal energy, U, may be related to the specific heat at constant volume (cv).

What is the relation between mass and power per time? Power= Joules/second=(Newton×meter)/second. This means: Power/time=Joules/second^2=(Newton×meter)/second^2.

Calculating efficiency The efficiency of a device, such as a lamp, can be calculated: efficiency = useful energy out ÷ total energy in (for a decimal efficiency) or. efficiency = (useful energy out ÷ total energy in) × 100 (for a percentage efficiency)