When work (w) is done by the system, the sign of w is negative. But when it is done on the system, the sign of w is positive, give reason.

When heat (q) is absorbed by a system, the sign of q is positive, and when it is rejected by a system, the sign of q is negative. Why?

An amount of work w is done by the system and q amount of heat is supplied to the system. By which the following relations the change in internal energy of the system can be expressed-

An amount of work w is done by a system and q amount of heat is supplied to the system . By which of the following relations the change in internal energy of the system can be expressed ?

What does pressure-volume work mean? Why is it considered that work done by a system is negative but work done on the system is positive?

Why is the sign of DeltaH negative for an exothermic reaction and why is it positive for an endothermic reaction?

The internal energy of a system is U_(1) . In a process, work done by the system is W and heat accepted by the system is Q. At the end of the process, the internal energy of the system is

An amount of work w is done by a system and q amount of heat is supplied to the system. By which of the following relation the change in internal energy of the system can be expressed?-

For a closed system, determine the change in internal energy (DeltaU) when (a) q cal of heat is absorbed by the system and w cal of work is performed on the system (b) q cal of heat is absorbed by the system and w cal of work is performed by the system (c) q cal of heat is evolved by the system and w cal of work is performed on the system (d) heat is not absorbed or evolved by the system, but w cal of work is performed by the system.

Calculate the change in internal energy when- (1) heat released by the system is 200 J and work done on the system is 120 J (2) heat absorbed and work done by the system are 200 J and 120 J respectively (3) heat released and work done by the system are 200 J and 120 J respectively.

State the conditions under which the work done by a force is positive or negative.