What is the 1st law of thermodynamics in symbols? and what do those symbols mean?

Answer 1

The first law of thermodynamics is an expression of the universal law of conservation of energy, and identifies heat transfer as a form of energy transfer. The most common enunciation of the first law of thermodynamics is:

“The increase in the internal energy of a thermodynamic system is equal to the amount of heat energy added to the system minus the work done by the system on the surroundings."

dU = δQ - δW

where dU is the infinitesimal increase in the internal energy of the system, δQ is the infinitesimal amount of heat added to the system, and δW is the infinitesimal amount of work done by the system on the surroundings. The infinitesimal heat and work are denoted by δ rather than d because, in mathematical terms, they are inexact differentials rather than exact differentials. In other words, there is no function Q or W that can be differentiated to yield δQ or δW.

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Answer 2

delta Q = delta U + delta W

delta - change in

Q - the amount of energy put into the system (usually thermal energy)

U - the internal energy of the system

W - the useful work done by the system.

This is an expression of conservation of energy, which says that whatever energy goes into a system either stays in the system, comes out of the system, or both.

Example: If we add 120 J of energy to a system, and the work done by the system is 40 J, the internal energy of the system has gone up by 40 J.