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Physics (Core) Revision
Transcript of Physics (Core) Revision
Thermal Radiation is energy transfer by Electromagnetic Waves
All objects emit thermal radiation
The hotter the object is, the greater the thermal radiation emitted. Surfaces and Radiation:
Dark matt surfaces are better emitters of thermal radiation than light shiny surfaces (So why do we not have black radiators at home?)
Dark Matt surfaces are better absorbers of thermal radiation than light shiny surfaces Three Types of Heat Transfer:
Conduction - mainly in Metals
due to the free electrons metals have transferring the energy inside the metal easily.
Non Metals are poor conductors because they do not contain free electrons
Some materials are good insulators due to them having pockets of air trapped in them (Why does this fact make them a good insulator?) Convection - Mainly in liquids and gases
Heating a liquid or gas makes it less dense
Convection is due to hot liquid or gas rising and cold coming in to take its place! Radiation:
Does not need any atoms to work
Is how the Sun heats Earth! Stopping Heat Loss!
Small objects can lose heat more easily
How can we reduce heat loss in buildings? What is the rule of energy? (Know it, it will help in the rest of this section). ENERGY! Can you state the main 6 forms???
Th Types of Energy Useful Energy is energy in the PLACE we want it in the FORM we want it
So what is wasted energy?
All energy, once used, will end up being transferred to its surroundings as _ _ _ _ making it surroundings?????
As Energy spreads out, it becomes harder to use for further energy transfers..... Useful Energy! All Energy is measured in Joules (J)
The efficiency of a device is:
Useful energy transferred by the device/Total energy supplied to the device
Wasted Energy causes inefficiency! Electrical Devices and Electricity!
Electrical energy is energy transfer due to an electrical current
Know some uses of Electrical energy. What is the Unit of Power? - It is WATT or 1 J/s
Power = Energy transferred (J)/Time taken (s) Calculating the cost of electricity (kWh etc) The National Grid is a network of cables and Transformers
We use Step-Up transformers to increase the voltage to the grid voltage
We use Step-Down transformers to decrease the grid voltage down to safe home use
A High Voltage (HV) in the Grid, reduces energy losses and makes the system more efficient The National Grid - Know the basics. Know your Electricity Generating methods!
You need an advantage (at least 2 different ideas) and disadvantage of each system. The Electromagnetic Spectrum! Know the Dangers of Radiation
You have 20 minutes to get the Uses and Dangers of the most commonly used Radiations! Sometimes, Physics is an uphill struggle...........
But watch this and see how you get on! Radiation!
Know the 3 types and their dangers and uses!
(I am not going to add them to this prezi, as you should have this information in your ed's!)
Know what they are and where they come from
Know the uses and why
Know the Half Life - The number of unstable atoms and the activity decreases to half in one half-life. The Universe!
Is it expanding?
What proof do we have?
Are we all aware of it and ready for it?
This is a good point to hand over to you and do some topic research and discuss with your teacher! Do you now feel better about the exam???