Természettudomány 1 konzultáció

Periodikus jelenségek

Naptárak

Heat, thermodynamics

Energy

What is energy?

Energy Is the Ability to Do Work.

Thermodynamics is the study of the inter-relation between heat, work and internal energy of a system. 


internal
kinetic
chemical
potential
electrical
atomic

First Law of Thermodynamics

The change in a system's internal energy is equal to the difference between heat added to the system from its surroundings and work done by the system on its surroundings.

Energy can be changed from one form to another, but it cannot be created or destroyed.
 

Second Law of Thermodynamics:

It is impossible for a process to have as its sole result the transfer of heat from a cooler body to a hotter one.

In any closed system, the entropy of the system will either remain constant or increase.

Entropy is the quantitative measure of disorder in a system.

work in greater than work out

Third Law of Thermodynamics:

As a system approaches absolute zero, it will eventually have to draw energy from whatever systems are nearby. If it draws energy, it can never obtain absolute zero. So, this state is not physically possible, but is a mathematical limit of the universe.

Three ways in which the heat can travel

Conduction

conductor, insulator
to trap air
to reduce
U- values

A U value is a measure of heat loss in a building element such as a wall, floor or roof. It can also be referred to as an ‘overall heat transfer co-efficient’ and measures how well parts of a building transfer heat.

Lost heat per second = U-value * area * temperature difference

 window double glazed 3
window single glazed 5.6
wall with air cavity  1.5
wall with insulation in cavity 0.5

Convection

chimney
sea breeze


Radiation

dull black
bright shiny
silver paint
greenhouses
vacuum flask

fur side inwards