energy Flashcards
define specific heat capacity
the energy required to heat 1 kg of a substance by 1 degree
what is the practical to investigate specific heat capacity
- measure mass of the block of chosen metal.
- wrap it in an insulating layer to reduce energy transferred to surroundings.
- insert thermometer into hole with drop of water to increase thermal contact
- record initial temperature.
- insert heater, connect to power supply and ammeter
- set p.d to 10v, and start stopwatch.
- current does work on heater, which transfers energy to thermal energy store of metal
- record temperature every min for 10 mins, ensure p.d is constant.
calculate power using P = VI
calculate energy transfer using E = Pt (s)
plot energy transferred to temperature graph. draw line of best fit
calculate shc using 1/(gradient x mass)
unit for specific heat capacity
j/kg°c
how to investigate effectiveness of different thermal insulators
- transfer 80cm^3 boiling water from kettle into a sealable beaker
- record initial temp and start stopwatch
- record temp every 3 mins for 15 mins
- pour out water and allow beaker to return to room temp
- repeat, wrapping beaker in different materials each time. ensure mass of water and insulator is the same
- plot table and compare
define power
rate of work done/energy transferred
when might an equation not be useful when calculating elastic potential energy
when limit of proportionality reached
(extension no longer directly proportionate to force applied)
Describe the energy changes involved
when a pendulum swings
upward: ke converted to gpe
peak: maximum gpe, zero ke
downward: gpe converted to ke
friction from pivot and from air resistance means energy is wasted via thermal energy stores, so pendulum swings with less energy and eventually stops
Describe the energy transfers for a bungee jumper.
falling: GPE is converted to KE
cord tightens: KE is converted to epe
cord recoils: epe converted to ke
ascends: ke converted to gpe
friction of air resistance means energy is wasted via thermal stores, jumper will not return to exact height
examples for chemical energy stores
food, fuel, batteries
what is waste energy
energy stored not for desired purpose
what is conduction
where vibrating particles transfer energy to neighbouring particle
what is convection
where energetic particles move away from hotter regions into cooler regions
ways to reduce waste energy and increase efficiency
lubrication
insulation, eg use material of lower thermal conductivity
what is the only thing that is 100% efficient and why
electric heaters: all energy in electrostatic energy store is transferred to thermal energy stores (useful)
three methods to reduce rate of thermal energy loss in a building
double glaze windows
loft and wall insulation
thicker walls
all lower thermal conductivity
how to improve efficiency of a robot with moving parts
lube it up
renewable vs non renewable
renewable is replenished as it is used, whereas non renewable will run out
uses of energy
transport
electricity
heating
examples of non renewable resources
fossil fuels:
coal
oil
gas
advantages of fossil fuels
- reliable, provide when needed
- produce large amounts
- relatively cheap
- versatile, many uses
disadvantages of fossil fuels
- emits large amount of CO2
- non renewable
- other pollutants produced eg sulfur dioxide, which causes acid rain
examples of renewable resources
solar
wind
tidal
hydro electric
geothermal
bio fuel
advantages of nuclear power
- no co2 emission when running
- reliable
disadvantages of nuclear power
- holds highly dangerous radioactive material, risk of being released & harming people
- produces large amounts of highly dangerous waste, stored for thousands of years before its safe
- must be decommissioned when no longer used, extremely expensive
how has the UK’s use of coal changed
- abundantly used up to 1950s
- then nuclear power produced 20% UK electricity by 1980
- became major producer of gas, by 2000 gas used as much as coal
- study into climate change led to 2005 kyoto protocol to reduce greenhouse gas emissions
coal vs gas
- gas has less co2 emission
- gas power stations have short start-time during high demand, coal is very long
advantages of renewables
- never run out, sustainable
- no emissions while running
disadvantages of all renewables
- non renewable is more efficient and economically beneficial, as it is cheaper and holds jobs
- only produce electricity, majority of uk use petrol cars (fossil fuels)
disadvantages of renewables like solar, wind, tidal
- depend on natural factors, unreliable supply
- non renwable is more efficient and economically beneficial, as it is cheaper and holds jobs
- visually or audibly obstructive
advantages and disadvantages of HEP
- very reliable
- habitats destroyed from building dams and clearing for reservoirs
- only useful in places with rivers, unlike uk
advantage and disadvantages of tidal barrages
- very reliable
- could damage wildlife
advantages and disadvantages of wave power
- very reliable, good potential in uk due to extensive coastline
- small scale
advantages and disadvantages of biofuels (plant material)
- carbon neutral, as burning releases co2 but plants grown take in co2
- produces gas, highly used for transport
- forest cleared to grow plants
future of uk energy
- to combat unreliability of renewables, baseload needed to constantly supply electricity. nuclear power used, more built
- during high demand, gas-fired power stations provide emergency power
what are different compnenents measure in when calucating kinetic/gravitational/elastic energy
kinetic: speed m/s^2
grav: field N/kg
elastic: constant N/m
all lengths in m
all masses in kg
what is work done and how can it be done
energy transferred from one store to another. can be mechanical (force) or electrical (current)
