Question

A system absorbs ${10}^{3}cal$ of heat and the system does $1677.3J$ work. The internal energy of the system increases by $2515J$. The value of J is

• A. $4.19J/cal$
• B. $4.18cal/J$
• C. $42J/cal$
• D. $420J/cal$

Answer 1

Answer: (A)

$4.19J/cal$

$1000$ calories $=4.184\times 1000$ Joules$=4184J$.
Work done is given as $1677.3J$.
And change in internal energy is given as $2515$ Joules. Thus using first law we have the heat absorbed as $1677.3+2515=4192.3J$. Thus we get the value of J as $4192.3/1000=4.192J/cal$