Two bodies $A$ and $B$ are placed in an evacuated vessel maintained at a temperature of $27 °\mathrm{C}$. The temperature of $A$ is $327 °\mathrm{C}$ and that of $B$ is $227 °\mathrm{C}$. The ratio of heat loss from $A$ to $B$ is about

Two 'spheres $\mathrm{P}$ and $\mathrm{Q}$ of same colour having radii $8 \mathrm{cm}$ and $2 \mathrm{cm}$ kept at temperature $127^{\circ} \mathrm{C}$ and $527^{\circ} \mathrm{C}$ respectively. The ratio of the energy radiated by $P$ and $Q$ in the same time is

Assertion: Perspiration from the human body helps in cooling the body.

Reason: A thin layer of water on the skin enhances its emissivity.

According to Newton's law of cooling, the rate of cooling of a body is proportional to ${\left(∆\theta \right)}^n$, where $∆\theta$ is the difference of the temperature of the body and the surroundings, and $n$ is equal to 

A bucket full of hot water cools from $75 °\mathrm{C}$ to $70 °\mathrm{C}$ in time $T_1$, from $70 °\mathrm{C}$ to $65 °\mathrm{C}$ in time $T_2$ and from $65 °\mathrm{C}$ to $60 °\mathrm{C}$ in time $T_3$, then

A liquid cools from $70 °\mathrm{C}$ to $60 °\mathrm{C}$ in $5$ minutes. If the temperature of the surrounding is constant at $30 °\mathrm{C}$, then the time taken by the liquid to cool from $60 °\mathrm{C}$ to $50 °\mathrm{C}$ is 

An object is. cooled from $75 °\mathrm{C}$ to $65 °\mathrm{C}$ in $2 \mathrm{minutes}$ in a room at $30 °\mathrm{C}$. The time taken to cool another object from $55 °\mathrm{C}$ to $45 °\mathrm{C}$ in the same room in $\mathrm{minutes}$ is

A body cools from $100 °\mathrm{C}$ to $70 °\mathrm{C}$ in $8$ minutes. If temperature of surrounding is $15 °\mathrm{C}$, then time required for body to cool from$70 °\mathrm{C}$  to $40 °\mathrm{C}$ is