Question

What are the limitations of the 1st law of thermodynamics?

Answer 1

the bigger limitation of 1st law of thermodynamics is that it doesn't talk about the quality of energy.
it doesn't put a restriction of flow of energy..
doesn't tells about the direction in which it flows when they are in contact.
doesn't tell about the final temp. of two bodies when they are in direct contact.

Answer 2

Answer:

(i) 1st law does not indicate the direction in which the change can occur :

• When a bullet strikes a target, KE of a bullet is converted into heat energy. But heat energy developed cannot be converted back into mechanical energy of the bullet.

(ii) 1st law gives no idea about the extent of change :

• No heat engine can convert all heat energy received from source into mechanical energy.

(iii) 1st law gives no information about the source of heat :

• i.e., whether it is a hot or a cold body.