Question

A given system undergoes a change in which work done
by the system equals the decrease in its internal energy.
The system must have undergone
(a) isothermal change (b) adiabatic change
(c) isobaric change (d) isochoric change
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Answer 1

from first law of thermodynamics

dq=dw+du

and from this que. dw=-du so we have dq=0 , means the change in heat is zero during the whole process and this happens in adiabatic process only so correct option is (b) adiabatic process