Friday, 25 July 2014

Physics lesson (question, answers and notes)

1.Why did Kelvin came out with the Kelvin scale when there was already degree Celsius?
Ans:
The Kelvin scale is named after the Belfast-born, Glasgow University engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907), who wrote of the need for an "absolute thermometric scale". Unlike the degree Fahrenheit and degree Celsius, the kelvin is not referred to or typeset as a degree. The kelvin is the primary unit of measurement in the physical sciences, but is often used in conjunction with the degree Celsius, which has the same magnitude. Subtracting 273.16 K from the temperature of the triple point of water (0.01 °C) makes absolute zero (0 K) equivalent to −273.15 °C (−459.67 °F). Kelvin did not want negative temperature so he put his 0 at the lowest possible temperature, absolute 0 (-273 degree Celsius ). Celsius decide to put 0 as freezing point and melting point of water and 100 as the steam point and condensing point. (Learn to convert K to Degree Celsius and vice versa)

2.What is the smallest particle today?
Ans:
The electrons in the atoms.

3.The definition of temperature?
Ans:
Temperature is the measurement of hotness and coldness of an object.

4.The definition of thermal energy?
Ans:
Thermal energy refers to the internal energy present in a system in a state of thermodynamic equilibrium by virtue of its temperature. Thermal energy always flows from a region of higher temperature to a region of lower temperature. Net flow of thermal energy occurs only when there is difference in temperature.

5.What is the difference between temperature and thermal energy? 
Ans:
• Thermal energy is not a directly measurable quantity whereas temperature is a measurable quantity.
• The temperature of an object can take negative values depending on the unit system used to measure the temperature, but the thermal energy of a system cannot be negative.
• Temperature is measured in Kelvin whereas thermal energy is measured in Joule.
• An object can lose or gain thermal energy in a state transition without changing the temperature of the system.



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