Question

The first law of thermodynamics can be written as $\Delta U$ = q +w for an ideal gas. Which of the following statements is correct?

• A. $\Delta U$ is always zero when no heat enters or leaves the gas.
• B. $W$ is the work done by the gas in this written law.
• C. $\Delta U$ is zero when heat is supplied and the temperature stays constant
• D. $\Delta U=-W$ when the temperature increases very slowly

Answer 1

The correct option is C $\Delta U$ is zero when heat is supplied and the temperature stays constant

Option:A

When no heat enters or leaves, $\Delta Q=0$

Therefore, $\Delta U=W$

Hence, it is an incorrect option.

Option:B

It is given $\Delta U=Q+W,So,workisdoneonthegas.$

Hence, it is also an incorrect option.

Option:C

$\Delta U=n{C}_v\Delta T$

Since Temperature is constant,

$\Delta U=0$

Hence, C is the correct option.