34 University of South Alabama Physics: PH 104 Laboratory Manual 6.5 Discussion

Question

34 University of South Alabama Physics: PH 104 Laboratory Manual 6.5 Discussion Questions How can the results of this experiment be improved? 1. 2. Define specific heat. Specific heat of water is 4186 J/kg.K. How does this set water apart from the rest of materials listed? 3. Suppose that you are given samples of three metals: iron, copper, and silver. For this example, we can say that each metallic sample has the same mass. We then apply a certain amount of heat to each of the three samples. Assuming that we apply the same amount of heat to each object, which one will raise in temperature by 10 degrees first? Explain your answer.

Explanation / Answer

6.5

2 &3 )

The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius.

To handle the problem of different bodies absorbing different quantities of thermal energy when subjected to the same temperature change, the specific heat c of a body is defined as the amount of thermal energy Q required to raise the temperature of a unit mass of the material 1 0 C. In terms of the SI unit joules, the specific heat c of a body is defined as the number of joules Q required to raise the temperature of 1 kg of the material 1 0 C.

Thus, c = Q / mt

defined the specific heat by equation we can rearrange that equation into the form Q = mct

Equation represents the amount of thermal energy Q that will be absorbed or liberated in any process. Using equation it is now easier to explain the Tyndall demonstration. The thermal energy absorbed by each ball while in the boiling water is

QAl = mcAlt

Qiron = mciront

Qbrass = mcbrasst

Qlead = mcleadt

Because all the balls went from room temperature to 100 0 C, the boiling point of water, they all experienced the same temperature change t. Because all the masses were equal, the thermal energy absorbed by each ball is directly proportional to its specific heat. We can observe that

cAl = 900 J/(kg 0 C)

ciron = 452 J/(kg 0 C)

cbrass = 394 J/(kg 0 C)

clead = 130 J/(kg 0 C)

Because the specific heat of aluminum is the largest of the four materials, the aluminum ball absorbs the greatest amount of thermal energy while in the water. Hence, it also liberates the greatest amount of thermal energy to melt the wax and should be the first ball to melt through the wax. Iron, brass, and lead absorb less thermal energy respectively because of their lower specific heats and consequently liberate thermal energy to melt the wax in this same sequence. If the masses are not the same, then the amount of thermal energy absorbed depends on the product of the mass m and the specific heat c. The ball with the largest value of mc absorbs the most heat energy.

7.5

1. while using 1Hz frequency of standing wave, we can't hear because human hear can hear frequency from 20Hz to 20KHz. Below this frequncy we can't hear. These we call it as Infrosonic wave.

there are many animals who appear to hear and produce sounds well below our range, known as infrasound. These include:

2. There is no way to hear infrasound waves by human ear.

3.

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