First law of Thermodynamics is considered one of the most asked concept.
30 Questions around this concept.
Which of the following is incorrect regarding the first law of thermodynamics?
In a given process of an ideal gas dW=0 and dQ<0. Then for the gas
An ideal gas is taken via path as shown in figure. The net work done in the whole cycle is

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The first law of thermodynamics -
According to it, heat given to a system (Q) is equal to the sum of the increase in its internal energy (U) and the work done (W) by the system against the surroundings.
$$
\Delta Q=\Delta U+\Delta W
$$
or For cyclic process
$$
\sum \Delta Q=\sum \Delta W
$$
Drawback of the First law of thermodynamics -
Important points -
Q and W are the path functions but U is the point function.
The first law of thermodynamics introduces the concept of internal energy.
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