6.1.2 Conservation and dissipation of energy Flashcards
(28 cards)
Energy can be?
transferred usefully, stored, or dissipated, but cannot
be created or destroyed
what happens when there is energy transfers in a closed system?
there is no net change to
the total energy.
In all system changes energy is?
dissipated, so that it is stored in less
useful ways. This energy is often described as being ‘wasted’.
explain ways of reducing unwanted
energy transfers on a moving object/vehicle
1)lubrication- reduces the friction between the moving parts of a machine
2)using wheels-decreases the friction between an object and the surface over which it is moving
3)making vehicles streamlined reduces the amount of air resistance exerted on them
explain a way of reducing unwanted energy transfer in cables
using low-resistance cables in an electric circuit reduces the amount of energy dissipated as heat
the use of thermal insulation in a build reduces unwanted energy transfer. how?
reduces the rate at which thermal energy is transferred from it
The higher the thermal conductivity of a material the higher?
the rate of energy transfer by conduction across the material
what is one way to reduce energy loss in a house?
use cavity walls insulation(double wall with gap in the middle), polystyrene foam in these gaps we can reduce the rate of loss of heat energy from the house
why is polystyrene foam used in these gaps?
an excellent insulator which means that it is a pure conductor of thermal energy ,it has a low thermal conductivity.
single glazed windows have?
high thermal conductivity
what else can reduce loss of heat energy?(windows)
double or triple glazed windows can reduce the loss of heat energy as they have a low thermal conductivity
the large amount of energy that can be lost through the roof of a house can be reduced by the?
installation of a loft which reduces the rate at which thermal energy passes through
what is a final way you can reduce the rate of thermal energy transfer?
build house with thick walls
efficiency, units + how it can be written?
has no units , can be written as a decimal(0-1) or percentage(0-100%)
describe ways to increase the efficiency of an intended energy transfer.
-use a lid
-plastic walls
-streamlining the shapes of moving objects
-reducing friction by lubricating parts
The main energy resources available for use on Earth include:
fossil fuels (coal, oil and gas), nuclear fuel, bio-fuel, wind, hydroelectricity, geothermal, the tides, the Sun, and water waves
what is a renewable energy resource?
A renewable energy resource is one that is being (or can be) replenished as it is used
what do uses of energy resources include?
transport, electricity
generation and heating.
what energy resources are renewable?
biomass, tidal, hydroelectric, wind, solar, geothermal,
fossil fuels (non-renewable) are cheap and convenient but release?
greenhouse gases when burnt such as carbon dioxide which contribute to global warming
fossils fuels can release sulphur dioxide which can cause ?
acid rain and breathing problems in humans
nuclear (non-renewable)
-radioactive waste they produce has to be stored carefully
-risk of nuclear meltdown
-uranium and plutonium are used as he sources of energy in nuclear power stations
biomass (renewable)
-the heat released when biofuels are burnt is sued to generate electricity on a small scale or heat buildings directly
-biomass is carbon neutral (absorb coz from the atmosphere when growing + release it again when burnt)
tidal (renewable)
-can produce large amounts of electricity in a reliable way
-expensive to build
