Question

What would be the work done on/by the system if the internal energy of the system falls by 100 joules even when 200 joules of heat is supplied to it

Answer 1

We have to calculate the work done on/by the system if the internal energy of the system falls by 100 joules even when 200 joules of heat is supplied to it.
Solution:
By sign convention,
dQ = du + dw  .......... (1)
du = 200 J  ( ∵Heat absorbed is positive )
dw = - 100 J   ( ∵Heat given out is negative )
Substitute these values in (1):
dQ = 200 - (-100)
dQ = 200 + 100
dQ = 300 J
This is the required answer.
Thanks.

Answer 2

We have to calculate the work done on/by the system if the internal energy of the system falls by 100 joules even when 200 joules of heat is supplied to it.

Solution:

By sign convention,

dQ = du + dw .......... (1)

du = 200 J ( ∵Heat absorbed is positive )

dw = - 100 J ( ∵Heat given out is negative )

Substitute these values in (1):

dQ = 200 - (-100)

dQ = 200 + 100

dQ = 300 J