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?

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.

A system is said to be an isolated system when it is

In a certain process. 678 J of heat is absorbed by a system, while 294 J of work is done on the system. What is the change in the internal energy for the process?

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.

In a process A to B to C to D , the heat absorbed by the system in the steps A to B and B to C are q_(1) and q_(2) , respetively, and the heat released by the system in the stp C to D is q_(3) . If q_(1)+q_(2)+q_(3)=0 , then will the process be adiabatic?

In a process, 600J of heat is absorbed by a system and 300J of work is done by the system. Calculate the change in internal energy of the system.

In a process, 701J of heat is absorbed by a system and 394 J of work is done by the system. What is the change in internal energy for the process?

A closed system participates in the following process: A to B to C . In the step AtoB , heat absorbed by the system =q cal and in the step B to C , heat released by the system=q cal. Therefore, in this process the sum of the heat absorbed and heat released by the system is zero. is this an adiabatic process? Given reason.

In Vaporisation of water, the signs of q and w are _____ and _____respectively.

Figs, (a) and (b) show the field lines of a positive and negative point charge respectively. Give the sign of the potential energy difference of a small negative charge between the points .Q and P, A and B.