AIM:
To study the relationship between the temperature of a hot body and its time of cooling by plotting curve.
APPARATUS:
Copper calorimeter, stirrer, wooden box with clamp and stand, a wooden lid having a hole in the middle, thermometer, stopwatch,hot water of about 80º c.
PRINCIPLE:
According to Newtons’s law of cooling,
dQ/dt α (T-Tο)
For a body of mass m, specific heat s, temperature T kept in surrounding of temperature Tο.
Q=msT
Now the rate of cooling,
dQ/dt=ms dT/dt
Hence, ms dT/dt α (T-Tο)
Since the mass and the specific heat of the body are taken as constant, the rate of change of temperature with time can be written as ,
dT/dt α (T-Tο)
The above equation explains that, as the time increases, the difference in temperatures of the body and surroundings decreases and hence, the rate of fall of temperature also decreases
PROCEDURE:
Place the calorimeter inside wooden box, fill hot water(80°) about 2/3rd of the calorimeter .close the wooden box, then suspend a thermometer inside the water and stir it continuously.When the temperature falls to 70º c start the stopwatch and note the temperature at every five minutes.Continue the observation till the temperature become constant. Plot the graph between time along x_axis and temperature along y_axis.This graph is called the cooling curve.
RESULT:
Cooling curve of liquid is plotted.
The graph is a exponential curve.
PHYSICS_WORLD 