Embibe Experts Solutions for Chapter: Heat Transfer, Exercise 1: TS EAMCET - 5 August 2021 Shift 1

Two rods whose lengths are $l_1$ and $l_2$ with heat conductivity co-efficients $k_1$ and $k_2$ are placed end to end. The heat conductivity coefficient of a uniform rod of length $l_1+l_2$ whose conductivity is same as that of the system of these two rods is

Statement $A:$ Convection involves flow of matter within a fluid due to unequal temperatures of its parts.

Statement $B:$ A hot bar placed under a running tap water loses heat due to effect of convection within water.

Statement.$\mathrm{C}:$ Heat transfer always involves temperature difference between two systems.

Two spheres of same material and radii $5 \mathrm{m}$ and $2 \mathrm{m}$ are at temperature $200 \mathrm{K}$ and $250 \mathrm{K}$ respectively. The ratio of energies radiated by them per second is

Thermopile Bolometer is used to detect

The wavelength of the radiation emitted by a black body is $6 \mathrm{mm}$ and Wein's constant is $3\times {10}^{-3} \mathrm{mK}.$ Then temperature of black body is

A body cools from $70 °\mathrm{C}$ to $40 °\mathrm{C}$ in $5$ minutes. Calculate the time it takes to cool from $60 °\mathrm{C}$ to $30 °\mathrm{C}$. The temperature of the surroundings is $20 °\mathrm{C}$.

A body cools from $70°\mathrm{C}$ to $40°\mathrm{C}$ in $5 \min .$ Calculate the time it takes to cool from $60°\mathrm{C}$ to $40°\mathrm{C}.$ The temperature of the surrounding is $20°\mathrm{C}.$