Physics - Core Flashcards
Why are metals good conductors?
They have free electrons which pass the current on by vibrating against other free electrons and ions/atoms they collide more often making the current go through quicker
What is conduction?
The process of vibrating particles passing on their kinetic energy to neighbouring particles
Name the three ways in which heat energy can be transferred
Radiation, conduction and convection
Explain the green house effect
Th sun produces short wavelengths that can pass through the atmosphere and heat objects, but the heated objects produce long wavelengths that cannot escape the atmosphere heating the earth up
What is the u-value?
The rate at which heat can transfer through a material
What is specific heat capacity?
Show us how much energy a substance can store
What are the factors that increase the rate that a object can be heated up?
- the temperature difference
- the material that it is in contact with
- shape
- surface area
How does a vacuum flask keep insulated?
Double walled - prevents conduction convection
Silver walls - prevent heat loss be radiation
Insulating foam - conduction
Stopper - reduces heat transfer
What is convection?
The movement of particles in a fluid
What happens in a convection current?
The particles in the hotter region have more energy and move faster so therefore diffuse and become less dense, they rise above the cooler ones which have little energy and are sinking they then get heated again, this is a convection current
Explain the kinetic theory
Solids - strong attraction forces which keeps them in regular arrangement little energy so vibrate in fixed positions
Liquid- weaker attraction forces but still close together, have some energy that lets them move in random directions and pass each other at slow speeds
Gas - no attraction forces, lots of energy so pass each other at high speeds in random directions
Explain the process on condensation
Gas cools so Particles loose energy Get denser and come together as there no longer able to overcome the attraction forces and then becomes a liquid
Explain the process of evaporation
The particles have enough energy and are going fast enough to leave the liquid but they must be going in the right direction
They leave the liquid lowering the average kinetic energy and temperature so the liquid cools
List types of energy that cannot be stored 6
Kinetic Light Sound Thermal Electrical Nuclear
Name the three types of energy that can be stored
Chemical
Elastic potential
Gravitational potential
What is the conservation of energy principle?
Energy can be stored, dissipated or change from one form to another, but never can it be created or destroyed
What is useful energy
Energy that is where we want it in the form that it is wanted
What happens to wasted energy?
It dissipates into the surroundings
Why can no machine be more than 100% efficient?
Because you cant get more out than what you put in
Name the 4 non renewable sources of energy
Oil
Natural gas
Coal
Nuclear fuel
Name the 8 renewable sources of energy
Food Wind Solar Wave Hydroelectric Geothermic Biofuels Tide
What does a step up transformer do?
Increases voltage and lowers current
What does a step down transformer do
Decreases voltage and increases current
What happens to the carbon in carbon capture and storage?
Goes to gas fields and oil fields
Give impacts that non renewable energy sources cause
Oil spillages Quarrying ruins landscapes Sulfur dioxide Pollution Nuclear waste
Name the waves in the electromagnetic spectrum
Radiowaves Microwaves Infrared Visible light Ultraviolet X- rays Gamma rays
What happens in optical fibres?
Infrared and visible light waves carry data over long distances, pulses of light are reflected of the sides of a narrow core from one end of the fibre to the next
+safer as it stays in fibre
+ more data is passed through
How is visible light used in a camera?
Light film sensor
Aperture controls how much light is let in
Shutter speed controls how much time the light is exposed to the film
Whats the difference between microwaves and radio waves?
Microwaves are shorter and dont spread out as much so they can pass through the earths atmosphere
What is the doppler effect?
The doppler effect is the change in wavelength and frequency of waves from a moving source towards or away from the viewer
Towards: increased frequency and shorter wavelength
Away: decreased frequency and longer wavelength
What is cosmic background radiation?
High gamma radiation that was left after the big bang
What is red-shift?
An increase in the wavelength of electromagnetic waves from a star or galaxy due to its motion away from us, the faster the speed the greater the wavelength
What is blue-shift?
A decrease in the wavelength of electromagnetic waves emitted from a star or galaxy due to its motion towards us, the faster the speed the shorter the wavelength
How does red-shift prove the big bang theory?
It shows that everything should have come from an original place if everything is expanding away from something
What is refraction?
The change in direction of a wave when it passes through a boundary of two substances
What is diffraction?
The spreading out of waves as it passes through a gap or an object
Name transverse waves
Electromagnetic waves
Ripples on water
Slinky spring
Waves on a string
Name some longitudinal waves
Sound waves
Ultra sound
Pushing the end of a slinky
What is the law of reflection?
The angle of reflection= angle of incidence
Why do electric storage heaters usually contain concrete or bricks?
The concrete and bricks have a high specific heat capacity so can store a lot of energy
Give ways in to increase the rate at which a gas condenses on to a surface
Increase density of the gas
Decrease temperature of the gas
Decrease temperature of the surface the gas touches
Increase the concentration of the gas by reducing airflow
Why can some particles evaporate from a liquid at a temperature lower than a liquids boiling point?
The particles in a liquid all have different kinetic energies, high energy particles that are near the surface of the water and are travelling in the right direction can have enough energy to escape the liquid and form a gas
How does cavity wall insulation help reduce heat loss?
Foam inserted into the gap will stop air from moving and forming convection currents
How does reflection work?
The light bounces off and in to our eyes
When/ how do you get a clear reflection?
When the light is travelling in the same direction and reflects from an even surface at the same angle
What are sound waves caused by?
Sound waves are caused by vibrating objects
Why can’t sound waves travel in space?
Because space is a vacuum and therefore there is no particles for the vacuum to vibrate off
What is a frequency?
The number of compete waves passing a certain point per second
What are the vibrations of a transverse wave?
In a transverse wave the waves are perpendicular at 90 degree angle to the direction of the energy transfer of wave
What are the vibrations of a longitudinal wave?
The vibrations are parallel to the direction of energy transfer of the wave
What happens when a wave goes from air to glass?
The wave goes toward the normal and the angle of refraction is smaller than the angle of incidence
What happens to a wave when it goes from glass to air?
The wave goes away from the normal and the angle of refraction is bigger than the angle of incidence
What makes diffraction bigger?
reducing the size of the gap and the gap between the waves/ wavelength
How does the doppler effect work?
When the object is moving towards you there is an increase in frequency and the wavelength is shorter, whereas when the object is moving away from you than the frequency is decreased and there is a longer wavelength
What happens when infrared is absorbed by the body?
It heats cells up and damages them
What are microwaves used for?
Satellite communication and mobile phones
What are the disadvantages for renewable sources?
Expensive
Not always reliable - wind
Only a small percentage of energy
How does a bungee jump work?
GPE>KE>EP>GPE+KE
Why do solar panels have matt black surfaces?
Matt black surfaces are the best absorbers therefore increase the rate of energy transfer
Why are insulators bad conductors?
They have large spaces between there particles this would reduce and slow the rate of energy transfer
