Flashcards in P1:Energy Deck (98):
When energy is transferred to an object, the energy is....
Stored in one of the object's energy stores e.g. kinetic energy store etc.
Kinetic energy is...
Thermal energy is...
The hotter the object, the more thermal energy
Chemical energy is...Example?
Anything that can release energy by a chemical reaction e.g. Food
Gravitational potential is...
Any object raised above ground level
Elastic potential is...Example?
Anything stretched e.g. springs, rubber bands
Example of electrostatic energy...
Two charges that attract or repel eachother
Example of magnetic energy...
E.g. Two magnets that attract or repel each other.
Nuclear energy is...
The nucleus of an atom releases energy from this store in nuclear reactions
4 ways energy can be transferred:
Mechanically, Electrically, By radiation, By heating.
Mechanically transferred energy happens when...
A force does work.
Electrically energy transferred happens when...
When a moving charge does work.
Energy can be transferred by heating - this is when...
Energy is transferred from a hotter object to a colder object.
Energy can be transferred by radiation - this is when...
Energy is transferred by e.g. Sound or light.
When a system changes...It can be transferred...
Energy is transferred. It can be transferred into or away from the system between different objects in the system or between different types of energy stores.
What is a system?
A single object or group of objects that your interested in.
What are closed systems?What is the net change like?
Where no matter or energy can enter or leave. The net change in the total energy of a closed system is always zero.
When a closed system changes...
There is no overall change in the total energy of the system.
Conservation of Energy Principle:
Energy can be transferred usefully, stored or dissipated but can never be created or destroyed.
When a system changes...
The energy is simply MOVED between stores. (Never disappears)
Is energy that is dissipated/wasted gone ?
No. It has just been transferred to an energy store that we didn't want.
What causes mechanical energy transfers?
2 points about Work Done:
- if a force moves an object, then work is done.- work done is the same as energy transferred.
What is the energy in an objects Kinetic Energy Store?The energy in the Kinetic Energy Store depends on...
Movement.The object's mass and speed - the greater its mass and the faster it's going, the more energy in the Kinetic Energy Store.
When an object speeds up, what happens to the energy?
It is transferred to the kinetic energy store.
Formulae for finding object's kinetic energy store:Units?
E = 1/2 x mass x speed (v) squared.Mass units - kgSpeed units - Minuites / secondsEnergy - joules
Formulae to find Gravitation Potential energy:Units?
E = Mass X gravitation field strength (9.8n/kg) x heigh Mass unit - kgHeight unit - m
Energy lost from the gravitation potential store = ?
Energy gained in the kinetic energy store (this is for a falling object when there's no air resistance)
Formulae to find elastic potential energy store:
E = 1/2 x Spring constant x extension squared.Spring constant unit - n/mExtension unit - m
What is specific heat capacity?
The amount of energy needed to raise the temperature of 1kg by 1 c. Basically, how hard it is to heat something up - some materials need more energy to be transferred to their thermal energy stores in order for their temperatures to increase.
The amount of energy stored or released as a material changes temperature depends on...
The specific heat capacity of the material.
Formulae for change in thermal energy:
= mass x specific heat capacity x temperature change.
Give the 9 steps to investigating the specific heat capacity of a SOLID BLOCK:
1) measure the mass of the block.2) wrap it in an insulating layer to reduce energy losses (e.g. thick newspaper)3) set up the apparatus. (connect ammeter and power supply to the insulation)4) measure the starting temperature of the block.5) turn on the power supply and start a stopwatch.6) record potential difference of the power supply and the current - they shouldn't change.7) after 10mins take a reading of the block's temprature.8) turn of the heater and work out the temprature change.9) work out the power using the equation.
What 3 things do you need before measuring specific heat capacity?
1) calculate the power.2) calculate the energy transferred.3) find the change in temperature.CALCULATE.
What is POWER?
The rate of energy transfer - the rate of doing work. Power is how fast energy is transferred.
What is power measured in?
One WATT =
1 joule of energy transferred per second.
Give the 2 equations you can use to calculate power:
1 POWER = ENERGY TRANSFERRED DIVIDED BY TIME.2POWER = WORK DONE DIVIDED BY TIME.
Explain how USEFUL energy is formed:
When energy is transferred between stores, some energy is transferred to the stores you want it in. USEFULLY TRANSFERRED.
What does it mean if energy is 'dissipated'?
This means the energy is transferred to useless stores which is often called 'wasted' energy.
Useless energy stores are usually....
Thermal energy stores.
There are ways you can reduce the amount of energy wasted.Explain how LUBRICATION REDUCES FRICTIONAL FORCES.
Friction acts between all objects that rub together which causes some energy to be dissipated. Lubricants reduce the friction between them which reduces the amount of dissipated energy.
There are ways you can reduce the amount of energy wasted.Explain how INSULATION helps.
When part of a material is heated - that part gains energy which is transferred across the material so the rest gets warmer. KNOWN AS CONDUCTION.Insulation has a low thermal conductivity so less transfers happen.
How quickly a building cools depends on: (3)
1) how thick the walls are - the thicker the walls the slower the building will cool.2) the thermal conductivity of the walls. Building walls from a material with a low thermal conductivity reduces the rate of cooling.3) how much thermal insulation there is - loft insulation reduces energy losses through the roof.
The less energy that is wasted, the more...
efficient the energy transfer is.
The efficiency of an energy transfer is a measure of....
The amount of energy that ends up in useful energy stores.
What are the 2 equations for efficiency:
Efficiency = useful output energy transferred DIVIDED BY total input energy transfer.Efficiency = useful power output DIVIDED BY total power input.
What are nonrenewable energy resources? Common ones?
Resources that will run out one day. The main ones are fossil fuels and nuclear fuel.
What are renewable energy resources?
Resources that will never run out because they can be replaced as quickly as they are being used.
Give the seven renewable energy resources:
1) SUN 2) WIND.3) WATER WAVES.4) HYDRO ELECTRICITY.5) BIO FUELS.6) TIDES.7) GEOTHERMAL.
Transport uses both renewable and nonrenewable energy resources. Give an example of each:
NON RENEWABLECoal is used to steam trains to boil water to produce steam.RENEWABLEVehicles can run on pure bio fuels or a mix of a bio fuel and petrol or diesel.
Electricity can also be used for transport. Give an example:
Electric cars and some trains.
Nonrenewable and renewable energy resources are needed for heating things. Give two examples of each:
NON RENEWABLECoal is burnt in open fireplaces.Gas fires burn natural gas to heat rooms.RENEWABLEElectric heaters can use electricity from renewable sources.Bio fuel boilers work in the same way as gas boilers.
State how wind turbines work: (2)
1) Placed in open spaces.2) When the wind turns the blades, electricity is produced.
Give two advantages of using wind turbines:
1) they produce no pollution once they are built.2) they do no permanent damage to the landscape because once they are removed the area goes back to normal.
Give two disadvantages of wind turbines:
1) they don't produce electricity when the wind stops.2) it is impossible to increase the supply when there is extra demand for electricity.
Where do you solar cells generate electricity from?
Directly from the sunlight.
Give two advantages of solar cells:
1) they create no pollution once they are built.2) in sunny countries they are very reliable.
Give two disadvantages of using solar cells:
1) A lot of energy is used to build them.2) The only generate electricity during the day.
Where does geothermal power get their energy from:
They use energy from the thermal energy stores of hot rocks below the Earth's surface. Used to generate electricity or to heat buildings.
Give 2 advantages of using geothermal power:
1) very reliable because the hot rocks are always hot.2) only a small impact on the environment.
How does hydroelectric power work?
It involves building a big dam across a valley, the valley is usually flooded and water is allowed to flow out through turbines which generates electricity.
Give two advantages of using hydroelectric power:
1) there is no pollution when it is running.2) there is no problem with reliability in countries that get rain regularly.
Give two disadvantages of using hydroelectric power:
1) animals and plants lose their habitats.2) there is a big impact on the environment due to the flooding of the valley.
How does wave power work to generate electricity?
Turbines are on the coast of turned by water waves and the electricity is generated.
Give one advantage of using wave power:
There is no pollution.
Give two disadvantages of using wave power:
1) they disturb the seabed and the habitats of animals.2) they are quite unreliable as the waves tend to die down when the wind drops.
How do TIDAL BARRAGES generate electricity?
Tidal barrages are big dams with turbines in them built across rivers. Water passing through the turbines generates electricity.
Give two disadvantages of using tidal barrages:
1) fish are killed as they swim through the turbines.2) they change the habitat of the wildlife e.g. Birds and sea creatures.
Give two advantages of using tidal barrages to generate electricity:
1) no pollution.2) they are reliable because we can predict the tides.
What are biofuels?
Fuse created from plant products or animal dung. They can be burnt to produce electricity in the same way as fossil fuels.
Give two disadvantages of using biofuels:
1) they release carbon dioxide when they're burnt.2) large areas of forest have been cleared to make room to grow biofuels so a lot of animals have lost their habitats.
Give two advantages of biofuels:
1) crops can be grown throughout the year.2) extra biofuels can be constantly produced and stored for when they are needed.
Give three ways in which nonrenewables create environmental problems:
1) fossil feels release carbon dioxide into the atmosphere when they are burnt which leads to global warming.2) coal mining makes a mess of the landscape.3) Oil spills cause environmental problems and harm sea creatures.
How have people began to use more renewable energy resources? (2)
Pressure from other countries and the public has meant that governments have set targets for using renewable resources.Car companies have began to be more eco friendly.
Moving to renewable energy sources can be limited by money, give 2 examples of this:
1) building new renewable power plants costs money.2) cars that run on electricity are more expensive than petrol cars.
Moving to renewable sources can also be affected by politics, people and ethics. Give two examples of this:
1) the cost of switching to renewable power will have to be paid through energy bills or taxes. (People)2) many people also did not want to live near to a power plant like a wind farm or hydro electric dam.
In real life, how does air resistance act against all falling objects?
It causes some energy to be transferred to other energy stores e.g. the thermal energy stores of the object and surroundings.
Explain what energy is useful and what energy is not with the example of a phone:
Phone = system. Energy is usefully transferred from the chemical energy store of the battery in the phone. Some of this is dissipated and energy is transferred to the thermal energy store of the phone.
Explain what energy is useful and what energy is not with the example of a cold spoon:
Cold spoon dropped in an insulated flask of hot soup which is sealed. The flask is a perfect thermal insulator so the spoon and soup form a closed system. Energy is transferred from the thermal energy store of the soup to the useless thermal energy store of the spoon (causing soup to cool down slightly) = energy transfers have occured but net change of energy is ZERO.
A poweful machine is one which....
Transfers lots of energy in a short space of time.
Heating can occur by...
Conduction and Convection.
Conduction takes place in...
Solids - especially Metals.
How does Heating by Conduction take place in solids?
It causes the particles to vibrate more and collied with eachother and during these collisions, energy is transferred between the particles' kinetic energy stores.
What is Thermal Conductivity?
A measure of how quickly energy is transferred through a material in Conduction.
Materials with a high thermal conductivity transfer...
Energy berween their particles at a higher rate.
Convection takes place in...
Gases and liquids - not solids.
What happens during Convection?
The warmer and less dense region (heat) will rise above denser, coolder regions. Energetic particles move away from hotter to cooler regions.
What happens to the particles during Convection?
An area is heated so the particles move even faster and the space between the particles increase. This causes the density of the region being heated to decrease.
Explain how Draught Excluders are an example of Thermal Insulation:
They are around doors and windows and reduce energy transfers by convection.
Explain how Double Glazed Windows are an example of Thermal Insulation:
They have an air gap between two sheets of glass to prevent energy transfer by conduction through the windows.
Explain how Loft Insualtion is an example of Thermal Insulation:
They reduce convection currents in lofts which is where the air particles are constantly heated, rising, cooling and then sinking.
Explain how Cavity Walls are an example of Thermal Insulation:
They are made up of an inner and outer wall with an air gap in the middle. The air gap reduces the amount of energy transferred by conduction through the walls.
Explain how CAVITY WALL INSULATION is an example of Thermal Insulation:
It is when the cavity wall air gap is filled with a foam which also reduces energy transfer by convection in the wall cavity.
How can you improve the efficiency of energy transfers? (3)
Insulating objects, lubricating them or making them more streamlined.
No device is...
100% efficient and most useless energy is transferred to the thermal energy stores.
What is the only exception to the idea that no device is 100% efficient?
Electrical heaters as all the energy in the electrostatic energy store is transferred to "useful" thermal energy stores.