Thermal physics is a huge topic in secondary school and JC physics that consists of concepts like transfer of thermal energy and thermal properties of matter. Often, students trip up because there are just so many concepts to remember, including formulae and application questions!
One of the biggest challenges when tackling thermal physics questions, especially in the realm of transfer of thermal energy, are the application questions. Knowing the concepts by heart isn’t enough – you need to truly understand it and recognise how it plays out in different real-life situations.
While some people can easily answer application questions using their ‘common sense’ and general knowledge, it is also worthwhile to be exposed to as many different types of scenarios so that you don’t get caught by surprise during the exams!
To help you with this, we will be running through multiple examples relating to transfer of thermal energy, including example questions and explanations.
Wool, thick fur, and feathers are nature’s clothing for animals, keeping them warm even during cold days. These fibres need to be fluffy as the trapped air acts as an insulator, reducing heat loss from the body.
Materials of cooking utensils
Cooking pots and pans usually have bodies made of metal (e.g. aluminum, iron, steel), and handles made of plastic or silicone. The base material needs to be a good conductor so that it can heat up quickly to cook the food. The handles are covered with an insulator of heat, so that the user will not be burnt by handling the cookware.
Think: When we want to boil a beaker of water, why do we place a metal gauze over the Bunsen burner before placing the beaker over it?
Placement of air-conditioning units
Notice how air-cons tend to be placed near the ceiling? This makes sense because dense, cool air sinks, circulating cool air around the room, while warmer air will rise and be cooled by the air conditioner. If the air-con is placed low in the room, the top of the room will remain warm as the cool air does not rise up. This principle is also the reason why heaters (in other countries) are usually placed near the ground.
Those who have spent a lot of time near the coast will realise that the direction of the breeze changes according to the time of the day.
In the day, when the surface temperature of the land is warmer than that of the sea, the warm air above land will rise. Cool air from above the sea will flow in to fill the space over land, forming a breeze blowing towards the land (“sea breeze”).
At night, the reverse occurs as the sea is warmer than land. As such, warm air over the sea rises, and cool air from the land flows towards the sea, resulting in “land breeze”.