Conduction

IMPORTANT

Conduction: Overview

This topic covers concepts, such as, Thermal Conduction, The Steady State Heat Flow, Appropriate Building Material for House & Appropriate Building Material for Nuclear Reactor etc.

Important Questions on Conduction

MEDIUM
IMPORTANT

A metal rod of length 2 m has cross sectional areas 2A and A as shown in the figure. The ends are maintained at temperatures 100°C and 70°C. The temperature at middle point C is___°C.

Question Image

HARD
IMPORTANT

The end A of a rod AB of length 1 m is maintained at 100 °C and the end B at 10 °C. What is the temperature (in °C) at a distance of 60 cm from the end B?

EASY
IMPORTANT

What kind of building materials is appropriate for thermal conductivity?

EASY
IMPORTANT

What quality is required for the ppropriate Building Material for Nuclear Reactor ?

EASY
IMPORTANT

 Heat transfer critical in nuclear reactors as Nuclear fission is heavily _____ reaction.

EASY
IMPORTANT

Heat transfer is critical for Nuclear reactors as nuclear fission is heavily exothermic reaction.

EASY
IMPORTANT

Why is heat transfer critical in nuclear reactors?

HARD
IMPORTANT

One end of a copper rod of length 1.0 m and area of cross-section 10-3 m2 is immersed in boiling water and the other end in ice. If the coefficient of thermal conductivity of copper is 92 cal /m-s-C and the latent heat of ice is 8×104cal/kg,then the amount of ice which will melt (in grams) in one minute is

HARD
IMPORTANT

One end of the copper rod of uniform cross-section and length 13.5 m is kept in contact with ice and other end with water at 100°C. At the distance 'x' (in meter) from 100°C water along its length a temperature of 400°C is maintained so that in steady-state, the mass of ice melting is equal to that of the steam produced in the same time interval. Write the value of 100x.

(Assume that the whole system is insulated from its surroundings. Latent heat of fusion of ice and vaporization of water are 80 cal g-1 and 540 cal g-1, respectively.

EASY
IMPORTANT

If the transmission of heat takes through molecular collisions, it is called

HARD
IMPORTANT

People prefer to give a layer of ____ on the ceiling so that heat transfer is prohibited and keeps the room cooler.

HARD
IMPORTANT

What should be done to prevent the transfer of heat through concrete roof during hot summer days?

HARD
IMPORTANT

What role does a layer of earth or foam provide on a house having a concrete ceiling during summer days?

HARD
IMPORTANT

Why do the houses made of concrete roof gets very hot during summer days?

HARD
IMPORTANT

In steady state heat conduction, the equations that determine the heat current jr [heat flowing per unit time per unit area] and temperature Tr in space are exactly the same as those governing the electric field Er and electrostatic potential Vr with the equivalence given in the table below.

Heat flow Electrostatics
Tr Vr
jr Er
We exploit this equivalence to predict the rate Q of total heat flowing by conduction from the surfaces of spheres of varying radii, all maintained at the same temperature. If QRn, where R is the radius, then the value of n is

MEDIUM
IMPORTANT

Heat is passed through two cylindrical rods of same material. Their diameters and lengths are in the ratio 1:2 and 2:1 respectively. If their ends are maintained at same temperature difference, the ratio of rate of flow of heat through them is

HARD
IMPORTANT

What is the rate of flow of heat through a tapering rod of length tapering from radius r1 and r2, when the temperature of the ends are θ1°C and θ2C and coefficient of thermal conductivity is K?

MEDIUM
IMPORTANT

An icebox almost completely filled with ice at 0°C is dipped into a large volume of water at 20°C. The box has walls of surface area 2400 cm2, thickness 2.0 mm and thermal conductivity 0.06W m1°C1. Calculate the rate at which the ice melts in the box. Latent heat of fusion of ice =3.4×105 J kg1.

HARD
IMPORTANT

Water is boiled in a container having a bottom of surface area 25 cm2, thickness 1.0 mm and thermal conductivity 50 W m1°C1. 100 g of water is converted into steam per minute in the steady-state after the boiling starts. Assuming that no heat is lost to the atmosphere, calculate the temperature of the lower surface of the bottom. Latent heat of vaporization of water =2.26×106 J kg1.

MEDIUM
IMPORTANT

The normal body-temperature of a person is 97°F. Calculate the rate at which heat is flowing out of his body through the clothes assuming the following values. Room temperature  =47°F, surface of the body under clothes =1.6 m2, conductivity of the cloth=0.04J s1m1°C1, thickness of the cloth =0.5 cm