Heat Conduction
Introduction and Literature Review
The study and analysis of the theory of heat transfer seeks to show the manner in which energy is transferred between bodies as a result of changes in temperatures. The energy transferred from one point to the other is defined as heat. There are three different modes of heat transfer which include radiation, convection and conduction (Persson, Lorenz, & Volokitin, 2010). Heat conduction can be described as the movement of heat through solids whereby the molecules collide. Heat moves from the hot end to the cold end of the metal. Convection on the other hand is the transfer of heat through fluids while radiation involves the movement of heat through vacuum spaces.
The main purpose of this experiment is to Help students in understanding the effect of different materials and their cross sectional area on heat transfer and conduction. The application of heat on a particular section of a material results in the transfer of heat through the material (Modest, 2013). However, this movement is based on the composition of the atoms. For instance, if a metallic spoon is left in a glass of hot water, heat will be conducted from the submerged part to the top making the entire spoon hot. Heat produced by boiling water will be spread through a room through convection. The movement of heat is referred to as thermal current. The speed at which the heat moves is mainly dependent on the composition of the atoms (Lienhard, 2013). As a result, the heat can either move very slowly if the atoms are very heavy or quite fast for light atoms. The dependence is mainly determined by the coefficient of thermal conductivity. Every material has its own unique value of thermal conductivity. Materials that have a high coefficient tend to absorb heat very quickly while those with a low coefficient absorb heat very slowly (Bejan, 2013). The table below shows thermal conductivity values for various materials.
Below is a chart of thermal conductivities for some common materials.
Material Coefficient of Thermal Conductivity (W/mK)
Air
Water
Glass
Concrete
Steel
Copper
0.026
0.609
0.8
1.0
46
401
Hypothesis
Heat conduction occurs in normal daily lives on different solids and fluid. The different rates of heat transfer can be attributed to variations in temperatures and the cross sectional areas of the materials involved. Heat conduction is faster in metals and materials with smaller cross sectional areas.
Method
Independent Variables
• Cross section of the metallic spoons
Dependent Variables
• Time taken by heat to move through the spoon
Control Variable
• Water temperatures
Materials and measurement tools
The following materials and tools were used for measurement: A beaker, water, plastic spoons, silver spoons, wooden spoons, copper spoons, timer, and margarine.
Procedure
The experiment was geared towards testing the thermal conductivity of different materials. Different materials including plastic spoons, copper spoons, and silver spoons with different cross sectional areas and length were collected for use in the experiment. Water was heated and placed in a plastic beaker. Each of the spoons was applied with margarine on one end before being dipped into the hot water on the other end. Care was taken to ensure that the spoons did not touch each other. The time taken by the margarine to melt on each spoon was recorded for further analysis.
Results
The results obtained from the experiment are shown in the table below
Table 1: Time taken by different materials to conduct heat
Spoon type Time (s) Cross sectional area (mm2)
Plastic spoon 1 69 6
Plastic spoon 2 64 4
Wooden spoon 1 72 6
Wooden spoon 2 70 4
Silver spoon 1 10 4
Silver spoon 2 9 2
Copper spoon 1 8 4.6
Copper spoon 2 6 3.2
Figure 1: Graph of the time taken by Different materials to conduct heat
Figure 2: Graph of Time vs Cross sectional area
Conclusions
From the results obtained, it is evident that the silver spoon with the smallest cross sectional area took the least amount of time to melt the margarine. This implies that silver is the best heat conductor and that materials with smaller cross sectional areas are better conductors of heat. The silver spoon was followed by the copper spoons, the plastic spoons, and the wooden spoons. Wood is the poorest conductor of heat. Therefore, the hypothesis that heat conduction is highly influenced by the material type and the cross section area is true.
The accuracy of the results could have been influenced by the amount of margarine placed at the end of each spoon, and the room conditions under which the experiment was conducted. For instance if too much margarine was placed at the end of one of the spoons compared to the other, it could have taken more time to melt. It is therefore recommended that the experiment should be conducted in a standard lab environment at room temperatures.
Theoretical studies show that silver is the best conductor of heat, followed by copper. From the experiment this has been shown to be true. Wood is a poorer conductor of heat compared to plastic materials, a fact which has also been proved to be true. Therefore, the results obtained agree with the theory on the conduction of heat in different materials.
References
Bejan, A. (2013). Convection heat transfer. John wiley & sons.
Lienhard, J. H. (2013). A heat transfer textbook. Courier Corporation.
Modest, M. F. (2013). Radiative heat transfer. Academic press.
Persson, B. N. J., Lorenz, B., & Volokitin, A. I. (2010). Heat transfer between elastic solids with randomly rough surfaces. The European Physical Journal E, 31(1), 3-24.
