Introduction to heat - class-IX

Metal conducts heat much better than wood does. Since your hand is hotter than room temperature, both the metal and the wood conduct heat away from it.an iron chair in winter feels colder

Mud houses have thatched roofs. The insulating effect of the thatch prevents heat from getting in very quickly (cool in summer) and heat getting out very quickly (warm in winter). Secondly, mud houses are made up of mud, which has large pores. As evaporation causes cooling, mud houses feel cooler in summer 

Heat can be transferred from one place to another by three methods: conduction in solids, convection of fluids (liquids or gases), and radiation through anything that will allow radiation to pass. The method used to transfer heat is usually the one that is the most efficient. If there is a temperature difference in a system, heat will always move from higher to lower temperatures.Heat will flow from Hot body to cold body

After touching ice, the hand's temperature drops. Any water warmer than the ice will feel warm to the hand. Since A, B, and C are at various temperatures (hot, cold, mixture), all will feel warmer than the ice-chilled hand.

A thermostat is a device that automatically regulates temperature, or that activates a device when the temperature reaches a certain point.

The Celsius and Fahrenheit scales intersect at -40 degrees. At this temperature, the numerical reading is the same on both scales.

Using the principle of calorimetry (heat lost = heat gained), we can determine the relative specific heats of the liquids. Solving the equations for the mixtures allows us to find the final equilibrium temperature when B and C are mixed.

(B)The triple point of a substance is unique, i.e. it occurs at one particular set of values of pressure and temperature. The melting point of ice and boiling point of water are not unique. They change with change in value of pressure or due to the presence of impurities in water.

The correct order of temperature of zones of candle flames is -
Outermost zone > Middle zone > innermost zone.
Because outerzone will have the highest temperature and inner zone will have the least temperature.

We know the relation between Fahrenheit scale and degree celsius,

${l _2} = {l _1}\left( {1 + {\alpha _A}\Delta T} \right)$

${l _2} = {l _1} + {l _1}{\alpha _A}\Delta T$

$\displaystyle {{{l _2} - {l _1}} \over {{l _1}}} = {\alpha _A}\Delta T$

$\displaystyle {{0.01 \times {{10}^{ - 2}}} \over {1 \times {{10}^{ - 2}} \times 25 \times {{10}^{ - 6}}}} = \Delta T$

$\Delta T = {40^0}C$

1 calorie: The amount of energy required to warm $1\ g$ of air-free water from $14.5^oC\ to\ 15.5^oC$ at a constant pressure of $101.325\ kPa$ $(1 atm)$

Answer is (A).

The S.T. unit of heat capacity is heat required per degree rise in temperature. So it is $JK^{-1}$

1 cal = 4.18 joules

The SI unit for energy, including heat energy, is the joule.

The therm (symbol, thm) is a non-SI unit of heat energy equal to100000 British thermal units (Btu). It is approximately the energy equivalent of burning 100 cubic feet (2.83 cubic metres) – often referred to as 1 CCF – of natural gas.

The amount of heat required to raise the temperature of one gram of water  through $ 1 ^{o}$ (from $14.5^{o}C$ to $15.5^{o}C$), is called one calorie.

According to the International Committee of Pure Physics, calorie is the standard unit to measure heat. The quantity of heat required to raise 1 gram of water from $14.5^o C \ to \ 15.5^o C$ is defined as a calorie.

We know,

The rate of loss of heat depends on the surface area and the emissivity. For a hollow sphere and a solid sphere of the same diameter, the surface area is identical. However, the hollow sphere has less mass, meaning it has a lower heat capacity and will cool faster.

The amount of heat required to raise the temperature of 1 kilo gram of water by $1:^oC$ is called kilo calorie.