The word ‘physics’ deals with energy and how energy interacts with everything around us. In Environmental physics, we apply the laws of physics to understand the environment. This environment can be natural or man-made which is also called built environment.
In this section, you will learn some concepts of basic environmental physics which have a number of applications. The understanding of these concepts will help you to appreciate ways in which heat transfer takes place. It is also required to design systems for human comfort.
When we heat a substance, molecules move randomly generating energy. Temperature is a measurement of this molecular or kinetic energy. Temperature is either measured on a Celsius scale or a Kelvin scale.
Celsius temperature (t) refers to melting point of ice and boiling point of water while Kelvin scale relates to absolute zero.
This is a measurement of the amount of moisture in the air: how ‘wet’ the air is. This wetness relates to amount of water vapours. Hence more humidity means more water vapours.
Relative Humidity measures the amount of water vapours present at a given temperature as compared with the maximum amount of vapours air can take. It is expressed as a ratio of the two quantities.
Dry bulb, Wet bulb and dew point temperatures
A dry bulb temperature refers to measurements taken with an ordinary thermometer. We can then make the bulb wet with, for example, with a gauze, and measure the surrounding temperature. As the moisture will evaporate, the readings will be lower than the actual. This gives an indication of how dry or wet the air is.
When air becomes fully saturated, the water vapour starts to condense. This temperature is called the dew point.
The publications listed contain a more detailed explanation of temperature and humidity. You are strongly advised to read these before attempting the tasks.
Some useful websites and video resources are listed with self explanatory titles which will help you understand these fundamental concepts.
This is the capacity of a system to carry out work. It can take many forms: Potential energy stored in a body; Kinetic energy generated due to motion; Sound energy; electromagnetic energy; and so on.
Sources of energy can be renewable (sun, wind, water, etc) or non-renewable (oil, gas and coal).
Heat and work are two forms of energy. It flows from a hot to a cold source.
Heat flows between the system and surroundings until the two are at the same temperature. When the system absorbs heat, the process is endothermic (it feels cold). When a system produces heat it is exothermic (it feels hot).
Under constant pressure, the heat absorbed or released is termed enthalpy or heat content. Enthalpy cannot be directly measured, but the change can be which is the heat added or lost by the system or change in enthalpy. It is thus the sum of the internal (heat) energy including the heat of the air and water vapours.
The publications listed contain a more detailed explanation of energy and its various forms. You are strongly advised to read these before attempting the tasks.
Some useful websites and video resources are listed with self explanatory titles which will help you understand the concepts. These also highlight the difference between energy sources and explain why renewable energy is important to us.