Flashcards in P1 Deck (57):
How is heat energy measured?
- Joules (J)
What is happening if an objects temperature rises?
- The object is taking in heat energy
What is happening if an objects temperature drops?
- the object is giving out heat energy
What 3 things does the energy needed to raise the temperature of an object depend on?
- the objects mass
- the change in temperature required
- the objects material
How do you calculate the amount of energy supplied?
Total energy supplied=
Energy supplied per second ✖️ number of seconds
What is Specific heat capacity?
- the value of how much energy an object can hold
- the energy needed to raise the temperature of 1kg of material by 1 degree
How do you calculate the amount of energy needed to raise the temperature of an object?
Mass(kg) ✖️ SHC(j/kg) ✖️ temperature change
How to you calculate specific heat capacity?
Specific heat capacity =
Energy ➗ (mass ✖️ temperature)
During the melting and boiling of water, what is the energy supplied used to do?
- to break intermolecular bonds as the water molecules change state.
What is Specific Latent Heat?
- the amount of heat energy required to melt or boil 1kg of a material
What doses specific latent heat depend on?
- the material
- the state
How do you calculate the energy required to boil or melt a certain mass of a material?
Energy = mass(kg) ✖️ specific latent heat
How do you calculate the payback time of an insulator?
Pay back time (years) =
Cost of product ➗ annual saving
What is a cavity wall?
- made up of an inner and outer wall with a cavity (space) full of air between them
How can heat loss be reduced from a cavity wall?
- by filling the space with air
What is energy efficiency?
- A measurement of how good an appliance is at converting input energy into a useful output energy
How can energy efficiency be calculated?
(Useful out put energy ➗ total input energy) ✖️ 100
What are the 3 ways that heat energy can be trNsferred?
What is conduction?
- the transfer of heat energy through a substance from a hotter region to a cooler region without any movement of the substance itself
Why are metals very good conductors?
- because they have free electrons which can move through the material carrying energy
What is convection?
- the transfer of heat energy from hotter regions to cooler regions by the movement of particles
What type of wave is light?
- transverse wave
What are the 3 features of a transverse wave?
> the maximum disturbances caused by the wave
> the distance between each wave
> the number of waves produced per second
What is the Electromagnetic spectrum?
- A continuos spectrum that extends beyond each end of the visible spectrum of light
What is the sequence of the Electromagnetic spectrum?
Radio waves ➡️ Microwaves ➡️ Infrared rays ➡️
Visible light ➡️ Ultraviolet rays ➡️ X-rays ➡️
How can you calculate the speed of a wave?
Frequency ✖️ wavelength
What speed do all electromagnetic waves travel at in a vacuum
- the same speed
What is diffraction?
- when the edges of a wave spread out as it passes through a gap or an opening
What is maximum diffraction?
- when the gap is the same width as the wavelength of the wave passing through it
- causes quality of image to reduce
When can light and infrared rays be reflected or refracted?
- when they cross a glass-air boundary
What does reflection and refraction depend on?
- the Angle of incidence
> if the angle is below the critical angle, the light or infrared is refracted away from the normal
> if the angle is above the critical angle the ray in totally internally reflected and not refracted
What are optical fibres and what are they used for?
- Long, flexible, transparent cables of a very small diameter
- used to send information in the form of pulses of light, or infrared radiation
- pulses aren't refracted, they are totally internally reflected
What is Electromagnetic radiation ?
- wireless technology
- used to send information without optical fibres
What is light used for communication produced by?
- a laser
What are the advantages and disadvantages of using Light to send information?
> travels very fast
> small loss of signal
> can't be wireless
What are the advantages and disadvantages of using Electrical to send information?
> can be sent along wires
> signal deteriorates
What are the advantages and disadvantages of using Radio waves to send information?
> can be wireless
> diffraction leads to signal loss
What are some uses of lasers?
- dental treatment
- cutting materials
- weapon guidance
- laser light shows
What are the waves like in laser light?
> have the same frequency
> are in phase with eachother
> have low divergence
What does 'in phase mean'?
- all the peaks and troughs match up
> waves in phase transfer a lot of energy
What does the amount of radiation that is absorbed or emitted from a surface depend on?
- surface temperature
- colour- black is good, white and silver are poor
- texture - dull is good, shiny is poor
What are the abilities of microwaves?
- are absorbed by water and fat molecules which causes them to heat up
- can penetrate about 1 cm of food
- can cause burns when absorbed by body tissue
- can travel through glass and plastics
- are reflected by shiny metal surfaces
What are the abilities of Infrared rays?
- used to heat the surface of food in cooking
- reflected of shiny surfaces
- absorbed by black objects
What can cause microwave signals to be lost or affected?
- large objects blocking the signal
- poor weather
- the curvature of the Earth
- interference between signals
What are infrared rays used in? (5)
- remote controls
- sensors for doors
- short distance wireless data links for computers or phones
- burglar alarms ( detecting body heat)
- security lights
What are Analogue signals?
- used to transmit signals
- vary continuously in amplitude
- can have any value within a fixed range
What are digital signals?
- used to transmit data as a series of pulses.
- do not vary, they have two states, on (1) and off (0)
What us multiplexing?
- when two or more digital signals are sent down the same optical fibre at the same time.
- enables more information to be sent in one go.
What are the advantages and disadvantages of wireless communication?
> no connections to a phone land-line needed
> portable, convenient! allows access anywhere
> aerial is needed to pick up signal
How are satellites used for global communication?
- a signal is sent from a ground station transmitter dish, to a satellite receiver dish.
- a return signal is then sent by the satellite transmitter to a ground receiver dish.
What is the Ionsphere?
- an electrically charged layer in the Earths upper atmosphere
- reflects longer wavelength radio waves
What does Refraction at the interfaces of different layers of the Earths atmosphere result in?
- Waves changing direction
- Diffraction at the edge of transmission dishes causes the waves to spread out, which results in signal loss
What are the advantages and disadvantages of DAB radio?
- more stations available
- less interference with other stations
- audio quality is not as good as FM broadcasts
- not available everywhere
What are seismic waves?
- shock waves produced by earthquakes
What are the two types of Seismic waves?
P-waves (primary waves)
- longitudinal and travel through both solids and liquids
S-waves (secondary waves)
- are transverse waves and travel through solids but not liquids. Travel slower than P-waves
What will happen to a wave as it passes from one medium to another?
- it will speed up or slow down