P1 Flashcards
Name 3 ways that heat can move
Radiation
Conduction
Convection
What are the laws of energy?
Energy is indestructible
It cannot be divided
It disapates
Cannot be destroyed only transferred
What is Conduction?
The process in which particles vibrate to pass on kinetic energy to neighbouring particles.
Why do metals conduct heat well?
Because there are free delocalised electrons available so they can conduct the heater faster throughout the metal.
Why are non metals not as good conductors?
Most don’t have free electrons therefore they warm slower so they are good insulators.
Why are solids good conductors of heat?
Becuase they are closely packed together so the energy is conducted quicker.
Why aren’t liquids and metals not good conducts?
This is becuase the particles aren’t held as tightly together so there are less collisions.
What is convention?
When more energetic particles move from a hotter region to a cooler one and take heat with them.
How do radiators heat a room?
They use Convection by heating the energy nearby and they then move to a cooler region.
How can you save energy in a house?
You use insulators which are expensive to install however they save money overall.
Name 4 ways of insulating a house.
Fitting loft insulation to stop Convection
Double glazing to take more time for Conduction
Silver foil to stop Conduction
And a cavity wall to slow convection
What would be the payback time if,
Cost of insulation was £60
Annual saving was £15?
15x4= 60
Therefore, it would take 4 years.
What are thermograms?
When you take an image of the heat inside. Like on police programs.
How does a microwave work?
The microwave creates the radiation which hits the food and makes it vibrate until it has conducted all the way through and cooked the food. It has a grill to stop microwaves escaping.
How do you calculate energy efficiency?
Useful energy
—————– X 100= x
Total energy
How do you know if a percentage calculation is incorrect?
If the answer is more than 100%
What is a sankey diagram?
A diagram that compares waste energy to useful energy.
What are the stages of heating ice?
Ice warming- gaining energy
Ice melting- energy is being used to break bonds so temp doesn’t rise
Water warms
Water is boiling- energy used to break bonds so temp doesn’t rise
Steam gets hotter
How do you calculate the energy in J (SHC)
SHC X Temp rise X mass that is heated (kg)=energy J/Kg oC
What effect does a high frequency have on the penetrating power?
It makes it more penetrating
What can waves pass through that particles cannot?
A vacuum
Why can’t particles pass through a vacuum?
Becuase there are zero particles inside the vacuum so they can’t pass thorough.
What are microwaves used for?
They are used for cooking and communication
How do cooking microwaves work?
The microwaves carry energy.
The waves and penetrate about 1 cm into the food
The fat and water molecules absorb kinetic energy and start to vibrate.
They don’t escape from the front due to a metal grid that reflects
How are microwaves used for communication?
They use line of sight and waves to travel long distances at the speed of light.
They are blocked by mountains and the curvature of the earth.
What are the types of waves in the electromagnetic spectrum?
Radio waves Microwaves Infrared radiation Visible light Ultraviolet radiation X-rays Gamma-ray
What is the speed of waves?
300,000 km/s
What is infrared radiation used for?
Optical fibre communication
What is Ultraviolet light used in?
They are used for sunbeds and increase risk of skin cancer
What are X-rays?
It is the name given when highly penetrating rays that emitted high energy electrons when they struck metal.
What are X-rays used for?
They are used in medical examinations.
What are Gamma rays used for?
They are used in killing malignant cancer cells
What is frequency?
How many waves there are a second
What is the equation for the speed of a wave?
Speed of wave (v) = frequency x wavelength
What are the three parts of 1 wavelength
Amplitude (loudness)
Trough
Crest
What is rat?
RULER
ARROW
TOUCHING
What is total internal reflection?
When the incident ray is greater than the critical angle
What is total internal reflection used for?
When travelling thorough optical fibres.
What do you need to get total internal reflection?
The medium outside must be less dense than material inside
It has to be greater than the critical angle
What is refraction?
Changing the speed of a wave when going to a denser medium so it changes its direction
