Energy Flashcards
(17 cards)
What types of energy stores are there and when a system changes how are they transferred
Energy stores: Thermal, Kinetic, Gravitational potential, Elastic potential, Chemical, Magnetic, Electrostatic and Nuclear.
A system is a single object or group of objects.
When a system changes, energy is transferred into or away from the system, between different objects or different types of energy.
Closed systems don’t allow matter, nor energy to enter or leave.
How can an energy be transferred
Heat- e.g. boiling water in a kettle: the water is the system, energy is transferred to the water into its thermal energy store from the kettle’s heating.
Charge flow- work is done against resistance in a circuit when a current flows.
Work done- a force moves an object e.g. throwing a ball upwards causes energy to transfer from chemical energy store of the arm to the kinetic energy store of the ball and arm.
What is the equation to calculate kinetic energy
Kinetic energy (J) =1/2 x mass (Kg) x speed squared (m/s)2
Ek= 1/2mV2
What is the calculation for gravitational potential energy
GPE (J) = mass (Kg) x gravitational field strength (N/Kg) x height (m)
Ep= mgh
What is the calculation for Elastic potential energy
EPE (J) = 1/2 x Spring constant (N/m) x extension squared (m)2
Ee= 1/2 Ke2
What is specific heat capacity
Specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1 degree Celsius.
Change in thermal energy (J) = mass (Kg) x SPC (J/Kg x degree Celsius) x temperature change (degree Celsius)
What are the steps for the specific heat capacity practical
Get a block of material with 2 holes, weigh it and wrap it in an insulating layer, insert the heater and thermometer into the holes.
Measure the initial temperature and set the P.D to 10V, turn on the power supply and start a timer.
Measure the temperature every minute and use the ammeter to make sure the current hasn’t changed.
After 10 readings have been made, turn off the power supply.
What is power supply (in terms of energy)
Power- the rate at which energy is transferred or the rate at which work is done and the watt as an energy transfer of 1 joule/second.
P=E/T, P=W/t
The energy transferred can be the same but if the time was longer, the power would decrease and if the time was shorter, the power would increase.
What is the conservation of energy principle
Energy can be transferred usefully, stored or dissipated but can never be created or destroyed, so the total energy in a system doesn’t change.
When energy is transferred, not all of it is done usefully and it may be dissipated (wasted)
E.g. in a phone, energy is usefully transferred from the chemical energy store of the phone battery but some is wasted to the thermal energy store of the phone when it warms up.
What is conductivity
The process where the vibrating particles transfer energy to neighbouring particles.
Energy transferred to an object by heating is transferred to the thermal store of the object.
When an object heats up, the particles vibrate and collide, causing energy to be transferred between particles’ kinetic energy stores; this continues through the object where the energy is transferred to the thermal energy store of the surroundings.
What are ways to reduce unwanted energy transfers
Lubrication- lubricants can reduce the friction of objects when rubbed together so this means less energy in the system is dissipated when they move.
Insulation- an inner and outer wall with air in the middle will reduce the energy transferred by conduction through the walls; loft insulation reduces energy loss by conduction; double glazed windows work the same as cavity walls- an air gap between two sheets of glass.
How to investigate the effectiveness of different insulators
Boil water and pour some into a beaker and lid, measure the mass of the water and use a thermometer to measure its initial temperature.
Seal it and leave it for 5 minutes.
Remove the lid and measure the water’s final temperature.
Pour away the water, so the container reaches room temperature.
Repeat the experiment but wrap the container in a material once its been sealed, using the same mass of water as before; find the temperature difference (and energy transferred) to have reduced once insulated.
What is efficiency
Efficiency= Useful power output/total power input.
No device is 100% efficient because the wasted energy is usually transferred to useless thermal energy stores, except electrical heaters.
Efficiency of energy transfers can be improved by insulating objects, lubricating them or making them more streamlined.
What renewable energy resources are there and what are they used for
Renewable (will never run out): Sun (solar), Wind, Water, Waves, Hydro-electricity, Bio-fuel, Tides, Geothermal.
Most damage the environment but not as bad as non-renewable but they don’t provide much energy and are unreliable.
Bio-fuels are used for transport and heating.
Geothermal and solar are used for heating.
What non-renewable energy resources are there and what are they used for
Non renewable (will eventually run out): Coal, Oil and Gas.
Will all damage the environment but are reliable.
Petrol and diesel are used for transport.
Gas and coal are used for heating
What are pros of moving towards using renewable energy
Burning fossil fuels damages the environment but renewable energies aren’t as harmful.
Non-renewable will eventually run out.
Public pressure to governments mean renewable usage has become a target but this puts pressure on energy providers to build new, profitable power plants.
Electric cars and hybrids are on the market and are very popular.
What are some cons of moving towards renewable energy
Scientists can’t make people and governments change their behaviour towards it.
Paying to make renewable energy plants is expensive and people can’t afford to pay if price increases.
People don’t want to live next to huge power plants.
Some renewable energies aren’t that reliable.
Researching improving reliability and cost is also expensive.
Making changes to these cost people money they can’t afford.
