Experiment 5 Heat Transfer

Experiment 5 Heat Transfer

Topic: Heat Transfer

Title: Thermal conductivity

Objective: To determine the thermal conductivity of glass

Theory:

The rate of heat flow through a conductor is expressed as 

        (1)

Where k is the thermal conductivity, A cross-sectional area of the conductor and the temperature gradient.

Rate of heat flow from the warm water with temperature 0 in the boiling tube to the surrounding is given by

........ (2)

wherem is the mass of water, c the specific heat capacity of water anddθdtthe rate of cooling.

Equating (1) and (2)

mc dθdt= -kAdθdx ........ (3)

From equation (3), if the surrounding temperature is 0 °C the relationship between temperature θ and time t is given by

= -ktBrx+ 0 ,

wheret is in second, 0 the initial temperature, B is 2.1 X 106 J m-3K-1, r the average radius of the boiling tube, and x the thickness of the wall of the boiling tube.

Apparatus:

i. A boiling tube

ii. A thermometer (-10 °C - 110 °C)

iii. A 1000 cm3 beaker

iv. Two stirrers

v. A cork stopper

vi. A stopwatch

vii. A pair of vernier calipers

viii. A retort stand and clamp

ix. Ice cubes 

x. Warm water 

Procedure: 

(a)    Measure and record the internal and external diameters of a boiling tube and hence calculate the average radius r and the thickness x of the wall of the boiling tube.

(b)    Fill up a beaker with water and ice. Clamp the boiling tube on to a retort stand and lower the boiling tube into the beaker until the whole of the boiling tube almost submerge in ice and water mixture as shown in the Figure 5.

Figure 5

(c)    Pour warm water into the boiling tube until the water level inside the tube reaches about 1 cm below the ice-water level in the beaker. The temperature of the ice and water mixture inside the beaker should be 0 °C before the warm water is poured into the boiling tube.

(d)    Insert the stirrer and thermometer through the cork stopper as shown in Figure 5.

(e)    Record time t and the corresponding temperature θ starting at temperature around θ = 30 °C. Record time t and temperature  until the temperature in the boiling tube reaches about 5 °C. The ice-water mixture in the beaker and warm water in the boiling tube should be constantly stirred throughout the experiment.

(f}    Plot a graph of In θ against t.

(g)    Determine the thermal conductivity of the glass. or alternative

Using interface PC thermometer , from "PCsensor" TEMPer1F

alternatif penggunaan jangka suhu

Data :

Graph :

Experiment 4 Static

Experiment 4 Static

Topic: Statics

Title: Density of an object 

Objectives: To determine the density of an object using a spring system.

Theory:

Figure 2. h must be constant

Figure E7- 2

Figure 2 shows forces acting at point Q where T the tension in the thread is,F 
is the tension in the spring and W is the weight of object A.

The equation below show the condition for equilibrium at point Q

Tsin =F,

T cos =W,

Hence,

w=F tan ……………(1)

From Figure 1,we have

tan =xh

For the spring,

F=k(l-l0),

Where kare the spring constant and l0 the unstretched length.

From equation (1),

W=k(l-l0)xh,

l=wkhx+l0 .

For constanth, the gradient s of graph l against x is proportional to  W .

The weight of object A,

W=VAg……..(2)

Where V are the volume and A the density of object A.

When object A is immersed in water, the up thrust acting on the object is given by 

Up thrust=W-W'=VWg………(3)

Where W' is the apparent weight of object A and Wthe  density of water.

Dividing equation (2) by equation (3),

(3)(2)WW-W'=AW,

A=ss-s'w……….(4)

Where s' is the gradient of graph l'against x'. 

Apparatus:

i. A spring
ii. Thread
iii. A pendulum bob
iv. An object A
v. A half-metre ruler
vi. Two retort stands with clamps
vii. Weights to stabilise stands
viii. A 500 cm3 beaker 

Procedure:

(a) Set-up the apparatus as shown in Figure 3. (Note: make sure that the spring is 
stretched such that it is just enough to be in horizontal position).

(b) Make a reference mark P on the thread which hangs the pendulum bob. This mark 
should be higher than the level where object  A is tied to the spring.

(c) Move the retort stand on the left to increase the angle B and adjust the loop until the 
spring is horizontal.

(d) Measure and record the corresponding length of the spring  L and horizontal distance 
from P to the thread x.

(e) Repeat step (c) for different values of L and x.

(f) Plot a graph of L against x.

(g) Repeat step (c) to (e) with object A immersed in a beaker of water.

(h) Measure and record the corresponding L’ and x', using the same range of x in step (e).

(i) On the same axes as in step (f), plot a graph of L’ against x'.

(i) Determine the gradients s and s'.

(k) Determine the density of the object A.

Data:

Graph: