work done on the system is positive or negative?

Answer 1

FIRST THERMODYNAMIC LAW STATES THAT "ENERGY CAN NEITHER BE CREATED NOR BE DESTROYED" for an isolated system.

TOTAL ENERGY= INTERNAL ENERGY +WORK DONE

ie, E[total] = E[internal energy] +P[pressure]* V[volume]

we cannot find" total internal energy" of the system,but can find find the
change in internal energy when the work is done

E[internal]= H[heat] + PV
^E[change in internal energy] = ^H + P^V +V^P

FOR AN ISOBARIC PROCESS[pressure is constant] ,^P=0
ie, ^E =^H + P^V
where P^V-work done

P^V is +ve when the" work is done on the system "because the system gets energy from outside & system has gain of energy.But if "work is done by the system",system has to spend its own internal energy and so its energy is lost & therefore it is -ve

Answer 2

Positive

Answer 3

Any Change in the Internal Energy of a System U is due to either the Heat Flow into/out-of the System or due to Work Done by/on the System provided the system's center-of-mass energy does not change.



It is important to observe that the D in DU is absolutely necessary because both work W and heat Q represent a transfer of energy where as the internal energy U is a quantity of energy that a system contains.
Another way to state his difference is that U is a state variable were as Q and W are not state variables. What this means is that if you take the system from one state to another state by two different processes, DU will be the same independent of the path taken but not Q or W.


The quantities Qin, Qout, Win, and Wout are all taken to be positive quantities where as Q and W can be either positive or negative

Answer 4

Depends how do u write the first law of thermodynamics.
If it is-
energy supplied = increase in internal energy + work done by the system (as in physics)
then work done by the system is +ve.
If it is-
energy supplied = increase in internal energy - work done by the system (as in chemistry)
then it is negative.

Answer 5

If your Q is related to physics here is the ans.-

Basic funda that work done by a force W = F. dr(both are vector)
This multiplication is a dot product of F & dr

[w] =F. dr*cosθ
now θ can tell you the sign of Work done

if Q is related to thermodynamics
then F =p*A
thus W =p*A*dr*cosθ=p*ΔV cosθ
simply
θ< 90 degree : W is positive
θ= 90 degree : W=0
θ> 90 degree : W is nageitive

Answer 6

work done on the system is +ve in physics

and -ve in chemistry

Answer 7

positive because it's done

Answer 8

positive....!! aleast u did some work