P1 Energy For The Home Flashcards
What is heat
A measurement of internal energy. It is measured on an absolute scale.
What is heat capacity
The energy needed to raise the temperature by 1 degree Celsius
What is specific latent heat
The energy needed to melt or boil 1kg of the material
Why is there no change in temperature when an object is heated and it changes state
Energy is needed to break the bonds that hold the molecules together, not hotness
How does double glazing reduce energy loss by conduction
Between the two panes of glass there is a vacuum, therefore the particles of gas are not there making it impossible to transfer energy
How does loft insulation reduce energy loss by conduction and conviction
Warm air in the home rises, air n the loft is warmed by the top of the ceiling and is trapped in the loft insulation, both sides of the ceiling are the same temperature so n energy is transferred
How does cavity wall insulation work
The air in the foam is a good insulator, the air cannot move by convection because it is trapped in the foam
How do insulation blocks reduce energy transfer by radiation
Energy from the sun is reflected back by the shiny foil to keep the home cool in summer, energy from the home is reflected back n to keep the house warm in winter
What is conduction
Due to the transfer of kinetic energy between particles
What is convection
When a gas is heated it expands making it less dense so it rises
What diagram is used to represent energy efficiency
Sankey diagrams
What is the amplitude of a wave
It is the maximum displacement of particles from its rest position
What is the crest of a wave
The highest point of the wave above its rest position
What is the trough of a wave
The lowest point of the wave below its rest position
What is the wavelength
The distance between 2 successive points on a wave
What is the frequency of a wave
The number of complete waves passing a point in one second
How does the electromagnetic spectrum, go
Radio - microwave - infrared - visible - ultraviolet - X-Ray - gamma ray
When does refraction occur
The speed of the wave decreases because it enters a more dense medium and increases when it enters a less dense medium
What is diffraction
The spreading out of waves as it passes through a gap
How does diffraction change depending on the size of the gap
The most diffraction occurs when the gap is of a similar size to the wavelength, larger gaps show less diffraction
What are a laser lights properties
It only has one frequency, is in phase and shows little divergence
How does a laser light read the surface of a compact disc
The surface of the CD is pitted, the pits represent the digital signal, laser light is shone onto the CD surface and the difference in the reflection provides the information for the digital signal
What happens if the angle of incidence is bigger than the angle of refraction
The light is reflected known as total internal reflection
What are the main uses of total internal reflection
In optical fibres for telephone conversations and computer data. And in an endoscope where a doctor can see inside a patients body as light is passed along the optical fibres illuminating the inside of the body, the light is reflected and passes up another set of fibres to either an eyepiece or a camera
How do microwaves cook food
The microwaves penetrate 1 cm into the food then the water and fat molecules vibrate more so the energy is transferred by conduction
How do normal ovens cook food
Energy is absorbed by the surface of the food causing kinetic energy to increase, then the rest of the food is cooked by conduction
How do satellites work with microwave communication
The signal form earth is received, amplified and retransmitted back to earth
What is necessary in terms of where the transmitter must be for microwave communication
They must be in the line of sight, so there is no obstacles in the way
What can change the signal strength of a microwave, however it doesn’t show a lot of diffraction
Adverse weather, large areas of water can scatter the signal and the curvature of the earth limits the line of sight
What is the disadvantages of mobile phones
It can interfere with sensitive equipment such as those in hospitals and planes
What happens when you press a button on a TV remote
A coded signal is sent to an LED at the front of the remote, this includes a start command, the instruction command, a device code and a stop command. The LED transmits in a series of pulses, which is decoded by the TV allowing it to do your commands
What are the benefits of digital over analogue
Improved signal quality for both picture and sound, a greater choice of programmes, being able to interact with the programme, information services such as programme guides and subtitles
What are the advantages of digital signals
The frequency of the carrier wave is usually higher, the combined wave is transmitted, interference from another wave can also be added and transmitted, if the wave is amplified, the interference is amplified as well therefore analogue is bad. However digital signals multiplex allowing a large number of digital signals to be transmitted at the same time
What is temperature
A measure of hotness on an arbitrary scale
Why do radio stations broadcast on a particular frequency, and why do some radio stations have the Same frequency
Because then there is no interference between 2 radio stations, however sometimes the radio stations are too far away to interfere with each other
What are the adv. and the disadvantages of DAB
Provides greater choice of radio stations however the quality isn’t as good
How do radio wave work
They behave like an optical fibre and undergo total internal reflection by reflecting off the ionosphere and water such as the oceans
What are some possible communication problems
Radio waves are diffracted when they wet an obstacle, refraction in the atmosphere needs to be taken into account when sending a signal to a satellite, transmitting aerial needs to be very focussed as the satellites aerial is very small, the beam is lightly divergent, some energy is lost form the edge of the transmitting aerial due to diffraction
What are the 2 different types of waves and what are their properties
P waves - refracted by the earths core, paths taken by these sows scientists the size of the earths core, travel through the e earth
S waves - not detected on the other side of the earth, won’t travel through liquid, tells scientists earths core is liquid
How does tanning occur
The tan is caused by ultraviolet light on the skin, cells in the skin produce melanin causing tan.
People with darker skin do not tan as easily because the ultraviolet radiation is filtered out
What happens penned to the ozone layer and why
The ozone layer is found in the stratosphere and it helps to filter out ultraviolet radiation, however it became very thin at the South Pole, this was due to CFC gases being used from aerosols and fridges. Happened because ozone depleting chemicals work best in cold temperatures
