The specific heat of hydrogen gas at constant pressure is $C_P = 3.4 \times 10^3 \text{ cal/kg } ^oC$ and at constant volume is $C_V = 2.4 \times 10^3 \text{ cal/kg } ^oC$. If $1 \text{ kg}$ of hydrogen gas is heated from $10^oC$ to $20^oC$ at constant pressure,the external work done by the gas is:

Check if the following statements are true or false:
$1.$ For an adiabatic process,$T V^{\gamma - 1} = \text{constant}$.
$2.$ The charging process of a battery is a reversible process.
$3.$ Water falling from a height is a reversible process.
$4.$ Internal energy,volume,and mass are intensive variables,while pressure,temperature,and density are extensive variables.

Helium gas undergoes a cycle $ABCDA$ (consisting of two isochoric and two isobaric lines) as shown in the figure. The efficiency of this cycle is nearly ....... $\%$ (Assume the gas to be an ideal gas).

For an ideal gas with initial pressure and volume $p_{i}$ and $V_{i}$ respectively, a reversible isothermal expansion occurs until its volume becomes $V_{0}$. Then, it is compressed to its original volume $V_{i}$ by a reversible adiabatic process. If the final pressure is $p_{f}$, then which of the following statement(s) is/are true?

Three moles of an ideal monatomic gas perform a cycle $ABCDA$ as shown in the figure. The temperatures of the gas at the states $A, B, C$ and $D$ are $400 \, K, 800 \, K, 2400 \, K$ and $1200 \, K$, respectively. The work done by the gas during this cycle is ($R$ is the universal gas constant). (in $R$)

Read the following statements:
$A.$ When the small temperature difference between a liquid and its surroundings is doubled,the rate of loss of heat of the liquid becomes twice.
$B.$ Two bodies $P$ and $Q$ having equal surface areas are maintained at temperatures $10^{\circ}C$ and $20^{\circ}C$. The thermal radiation emitted in a given time by $P$ and $Q$ are in the ratio $1:1.15$.
$C.$ $A$ Carnot engine working between $100 K$ and $400 K$ has an efficiency of $75\%$.
$D.$ When the small temperature difference between a liquid and its surroundings is quadrupled,the rate of loss of heat of the liquid becomes twice.
Choose the correct answer from the options given below: