Tuesday, 29 July 2014

Physics lesson (think4)

Thermal energy flows from a hotter region to a colder region until reach thermal equilibrium.

The greater the temperature difference, the faster the rate of transfer thermal energy.

Molecules are always moving at constant random motion.
Solid- only can vibrate at its position
Liquid- can move
Gases- moving faster
Molecules stop moving at absolute 0. 

Monday, 28 July 2014

Physics lesson (think3)

The tile is a better conductor of thermal energy than the parquet. The tile is conducting thermal energy away faster than the parquet. When thermal energy leaves the foot faster, the foot feels colder.

Friday, 25 July 2014

Physics lesson (think2)

When you come out of the swimming pool on a hot day, water on your body that evaporates at a faster rate bring more thermal energy away from the body. Water changes state, when there is a change in state in water from liquid to gas,it requires a lot of thermal energy to be removed from the body. On a hotter day, the rate of evaporation is faster thus you lost thermal energy in a shorter time so you shiver.

Why do people shiver when feel cold?
The human body needs to stay at the same temperature to survive - about 37 degree Celsius. When you feel cold, tiny sensors in your skin send messages to your brain telling you need to warm up. Your brain sends messages to nerves all over your body telling your muscles to tighten and loosen really fast, which is what we call shivering. It does this because when muscles move they generate heat.

Physics lesson (think1)

Physics lesson (question, answers and notes)

1.Why did Kelvin came out with the Kelvin scale when there was already degree Celsius?
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?
The electrons in the atoms.

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

4.The definition of thermal energy?
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? 
• 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.

Physics lesson (temperature and thermometer)

The above diagram is a thermometer with its labelled parts.Thermometer use physical properties of thermometric substances to measure temperature. 
Thermometric substances can be solids/liquids/gases and is continuous.

The above diagram shows the formula of how to get the temperature.

Physics lesson (group answers)

Our group answer
Standard answer in macro

Standard answer at micro