OCR Gateway Physics

Anna Raju
Flashcards by Anna Raju, updated more than 1 year ago
Anna Raju
Created by Anna Raju almost 5 years ago
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Temperature Temperature is the average kinetic energy of particles in a substance. It tells us how hot a substance is and can be measured in Celsius and Fahrenheit. It is an arbitrary scale so without a a thermometer you can tell that one object is hotter than another object
Heat Heat is a form of energy and is measured in joules like all forms of energy. Heat energy flows from a hotter place to a colder place until all places are at the same temperature
Thermogram A thermogram shows how much heat something is giving off, the hottest areas are white, red, yellow. The coldest areas are blue, dark purple
Specific Heat Capacity Specific heat capacity measures shows much energy a certain material holds. The specific heat capacity of an object is the energy needed to raise one kilogram of a material by 1 degree. Energy=Mass*SHC*Temperature change
Changing State When an object changes state any heat energy given to it will be used to break bonds instead of being used to raise the temperature.
Specific Latent Heat Specific Heat Latent is the amount of energy needed to change the state of 1 kilogram of a substance Energy=Mass*Specific Heat Latent
Conduction Conduction is how solids are heated. When solid particles are heated they will vibrate and as they vibrate they bump into other particles and cause them to be heated as well, this continues until the whole solid is heated
Conductors Liquids and gases are bad conductors as their particles aren't in a regular arrangement so its harder for the heat to passed on. Metals are good conductors.
Double Glazing Double glazing prevent heat loss by putting two layers of glass in a window which means that heat can't be lost through conduction. There is also a vacuum between the two layers
Convection Convection is how fluids are heated. When air is heated, by a radiator for example, it will rise above the colder air. Then the colder air will be heated and will rise and then a current will be formed
Cavity Wall Insulation Cavity wall insulations prevents heat being lost through convection currents inside walls
Infrared Radiation Infrared Radiation is the transfer of energy through electromagnetic waves. Certain surfaces absorb infrared radiation better than others, black,matt surfaces are better at absorbing heat than shiny light surfaces.
Payback Time Payback time is the time it takes to get the money that was spent on reducing heat loss. Payback Time = initial cost of installation/saving on energy bills every year
Efficiency Efficiency = useful energy output/ total energy input * 100
Features Waves The amplitude of an wave is the maximum height of the wave. The wavelength is the distance between a certain point on a wave and that point on the next wave. Frequency of waves measures how many waves pass a certain point in one second
Wave equation Wave Speed = frequency * wavelength
Electromagnetic Waves Electromagnetic waves do not need a medium like air and can travel in an vacuum. The shorter the wavelength and the higher the frequency of an electromagnetic wave, the more energy it will have.
Reflection All waves can be reflected and the law of reflection states that the angle of incidence is equal to the angle of reflection
Refraction Refraction is when light changes direction when it enters different medium
Diffraction Diffraction is the spreading out of waves after they move around an obstacle of through a gap. The amount of diffraction depends on the length of the wavelength and the size of the gap
Total Internal Reflection Total Internal Reflection happens when the angle that the light hits the boundary between two mediums is bigger than the critical angle of the material then all of all of the light will be reflected back and this can only happen of light is travelling in the denser medium.
Fibre Optics Total Internal Reflection is used in optical fibres to transmit large amounts of information, in a way that it is much faster than using normal phone lines and in endoscopes to look inside peoples' bodies.
Morse code Morse code is one of the first ways that light was used to send messages
Lasers Lasers are a narrow beam of light, that is monochromatic and in phase. They can be used in surgery and in dental treatments and and can be used to guide weapons
CDs In CD readers, CDs are read by using lasers, they contain a series of pits which contain information when lasers are reflected back they don't reflect the same out of light which leaves the computer a series of light impulses
Cooking with Infrared Infrared radiation is emitted by warm objects and this radiation reaches the surface of the food and heats it up and then through conduction the rest of the food will be heated up. Most grills and toasters have a shiny surface to reflect radiation back to the food
Cooking with microwaves In microwave ovens, microwaves will be absorbed by water and fat particles that are up to 1 cm into the food. This heats them up and they heat up the rest of the food through convection and conduction. The 1 cm means that the food warms up much faster. They also have shiny metal surfaces to reflect microwaves back to the food. Microwaves can cause burns to human and so to prevent microwaves from escaping microwave ovens they have a metal mesh on their door
Mobile Phones Mobile phones send and receive microwaves as they can be transmitted over very large distances but there must be a line of sight between the phone and the receiver.
Signal Loss If they are any obstructions such as hills and buildings then the signal may be lost. Signal can be lost if the microwaves have to travel over large surfaces of area and in poor weather conditions. Other electromagnetic waves can interfere with the microwave transmissions
Ways to reduce signal loss Place transmitters close together Place transmitters on high hills to avoid other obstructions
Dangers of mobile phones Mobile phones are seen to have a small heating effect in the brain. They may also be dangerous to people who live near transmitters as they may be affected by the microwaves
Different ways to transmit data signals Analogue have various values that continuously change Digital signals have only two signals, on and off and is a series of pulses
Digital Signals Advantages of digital signals are that as when digital signals are sent any interference can be removed easily to give a good quality of sound or image. Also various digital signals can be sent at the same time which means that more information can be sent at the same time.
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