NS Exam 30 Nov Flashcards
(101 cards)
When does heat transfer happen
The transfer only occurs if there is a temperature difference.
Name 2 things that insulating materials do
1) Help minimize heat loss in winter and heat gain in summer
2) They slow down heat loss or heat gain through convection, conduction, and radiation.
Name 2 insulating materials
Fabrics
Styrofoam
How do fabrics insulate
The woven fibers of the fabric trap air between them. Air is a poor conductor of heat and so it slows heat loss through the fabric.
How does styrofoam insulate
It is made from polystyrene which has had air pumped through it. This makes styrofoam extremely light and the air pockets make it a very good insulator.
Internal temperature is much higher than the surroundings, heat moves from our bodies to the environment
What is this called
Heat loss
What is the main source of heat energy on Earth
The main source of heat energy = radiation from the sun
Name 3 ways to save energy at home
1) Turn off unnecessary lights.
2) Change your light bulbs to energy-efficient bulbs.
3) Use a geyser blanket.
4) Unplug unused electronics.
5) Use extra blankets instead of a heater.
6) Turn the geyser off when you leave the house.
7) Only do full loads of washing or dishes.
8) Wash clothes with cold water.
How do solar water heating systems work
Hot water can be used directly or the steam can be used to turn turbines to generate electricity
Coldwater flows in the cold water intake pipe and then down the long tubes, called evacuated tubes. The water warms up due to energy transfer from the Sun and it then flows into the storage tank at the top. When someone wants hot water in the house, the hot water flows out of the hot water output and down into the house.
The water runs down the central heat pipe. There is an absorber plate below each pipe and this is enclosed within two layers of tube.
Between these tubes, there is a vacuum. This means that the Sun’s energy can still pass through to warm the water. However, when the energy is transferred to the water, and it warms up, the vacuum prevents energy from transferring back out by conduction or convection.
Underneath the heat pipe, there is a plate that helps to absorb radiant energy from the Sun and transfer it to the heat pipe
What is The energy which is transferred to the surroundings?
This energy is reffered to as wasted
What does a Sankey diagram do
Sankey diagram to show how the energy is transferred in a system
What are the 2main things in a Sankey diagram and where do they go
useful energy (arrow at the top) and wasted energy (arrow going to the bottom)
What is the input energy made up of
The width of both the output energy arrows (useful and wasted) add up to the width of the input arrow.
True or false
Sankey diagrams are drawn to scale
True
An efficient system is one where the useful output energy is only slightly (bigger/smaller) than the input energy
smaller
An inefficient system has a lot of wasted energy.
What is the formula for energy efficiency
Energy Efficiency = Useful Output energy
~~~~~~~~~~~~~~~~~~~~
Total input Energy
AT what % efficiency is the most efficient coal power station
The most efficient coal-fired power plants only operate at around 44% efficiency
When large chunks of coal are crushed into a fine powder. What is it called
This is called pulverization.
How is coal turned into electricity
The large chunks of coal are first crushed into a fine powder. This is called pulverisation.
The coal is then transported to a furnace where it is burnt.
Chemical potential energy ———> Thermal energy
The thermal energy from the burning coal is used to boil water and generate steam which is pressurised in the pipes
Thermal energy ———–> Kinetic energy
The steam pushes the blades of the turbine and so the turbine spins.
Kinetic energy ————-> Mechanical energy
Mechanical movement energy transfers from the turbine to the generator (rod/shaft)
The turbine is connected to the shaft of the generator which then rotates large magnets within wire coils, which generates electricity.
Mechanical energy ———-> Electrical energy
How does a generator work
A generator consists of a very large solenoid with a large rotating magnet. The solenoid is made up of thousands of coils of conducting wire. When the magnet is turned inside the coil, the generator produces electricity.
When is energy lost in a coal power station
The cooling tower where steam is lost.
Energy is also lost through the different energy transformations.
How does hydropower work
Falling water Turbines turning
Kinetic energy ——————-> Mechanical energy
Turbines turning the shaft which turns the generator
Mechanical energy ————>
Generator produces electricity
Electrical energy
How does wind make electricity
Exact same as hydropower but with wind as the kinetic energy
What are the Main Functions of the Sun relative to Earth
The Sun’s energy sustains life on Earth
Plants and animals depend on the Sun for warmth
The water cycle is dependent on the Sun’s energy
Stored energy from the Sun acts as a fuel
