Topic 1 Flashcards
state the law of energy conservation
energy cannot be created or destroyed, it can only be transferred into different forms
state any changes in total energy of a ball that’s been kicked, assuming no external forces act
total energy of the system remains constant due to conservation of energy
what is waste energy
energy not used by the device for its desired purpose, eg thermal energy in a lamp
describe energy changes that occur in a filament light bulb
electrical energy is transferred into light and heat energy
light is useful energy form, heat is waste
state two equations to calc efficiency
efficiency = useful total energy output/ total input energy transfer
efficiency= useful power output/total power output
how can efficiency be increased
reducing waste output by lubricating etc
recycling waste energy eg recycling thermal waste energy as input energy
state the consequence for energy transfer of a material with high thermal conductivity
the rate of energy transfer through the material is higher than for material with a lower thermal conductivity
do double glazed windows have a higher or lower thermal conductivity than single glazed ones
lower, meaning less energy transfers through them
what key factors affect the rate of cooling a building
thickness of walls and the thermal conductivity of the walls
three methods of reducing heat loss in a building are
double glazing, loft and wall insulation and by having thicker walls
how can efficiency of a mechanical machine with moving parts be improved
by lubricating moving parts to reduce friction and therefore energy loss due to heating
how can efficiency of a radiator be improved
by installing metal foil sheets behind radiator to reflect heat back into the room rather than it being absorbed by the walls
how can efficiency of boiling water in a pan be improved
by placing a lid to reduce heat loss from the top
how to find the wasted power
energy wasted divided by time
how to calculate total power input
useful power output and wasted power
