Question

Which of the following is a statement of the first law of thermodynamics?

A) Energy cannot be created or destroyed.
B) The entropy of the universe is decreasing.
C) The entropy of the universe is constant.
D) Kinetic energy is stored energy that results from the specific arrangement of matter.
E) Energy cannot be transferred or transformed.

Answer 1

The first law of thermodynamics states that the
`\fbox{Energy can neither be created nor be destroyed}`. So it only transforms from one form to another.

The option (A) is correct.

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•First law of thermodynamics can also be defined as ‘The amount of heat supplied to a system is equal to sum of change in internal energy of system and amount of external work done by the system’

•This actually means that energy can neither be created nor be destroyed.

•The mathematical expression is
`\fbox{dQ=dU+dW}`.

•This law has its limitations also , as it doesn’t tell about direction of flow or efficiency of conversion of heat.