Page 118 - Physics - XI

Thermal Properties of
7 Thermal Properties of
Matter
Matter

EXPERIMENT - 6

Aim

To study the relationship between the temperature of a hot body and time by plotting a cooling curve.

Apparatus and Materials Required
Newtonʼs law of cooling apparatus, two thermometers, a stopwatch, clamp stand, a beaker, a heater, and
two rubber stoppers with holes

Description of Apparatus
Thermometers
Clamp
Thermometer A

T Lid T Stirrer
Thermometer B 2 1
Calorimeter

Beaker

Stand Water
Double-walled container

Fig. 6.1: Newton's law of cooling apparatus

The apparatus for Newton's law of cooling is shown in Fig. 6.1. It has a double-walled container which is
closed by an insulating lid. The calorimeter is suspended inside the container. In between the double walls,
water is fi lled to keep the temperature of the environment surrounding the calorimeter constant.

Principle/Theory
Newton's law of cooling
Newton's law of cooling states that the rate of cooling (i.e. heat lost per second) of a body is directly
proportional to the diff erence in temperature of the body and its surroundings provided the diff erence of
temperature is not too large and all other conditions remain same.
Consider a body of mass m and specifi c heat s and temperature θ is placed in surroundings of temperature
θ . Then, according to Newton's law of cooling
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