energy resources and transfers

what are the 8 energy stores?

• chemical - in food, fuel or batteries

• kinetic - in a moving object

• gravitational - more in an object lifted above its planet

• elastic - in a stretched, squashed or twisted object

• thermal - in an object at high temperature

• magnetic - in magnetic forces between magnetic poles

• electrostatic - in electrical forces between charges

• nuclear - in the immensely strong forces in atomic nuclei

what are the 4 methods of energy transfer?

• mechanically - when a force acts and something moves

• electrically - when a current flows

• by heating - because of a temperature difference

• by radiation - a wave such as light microwaves or sound

what is the principle or conservation of energy

energy cannot be created or destroyed, but it can be transferred from one form to another or stored

describe how thermal energy can be transferred by conduction

through direct contact between particles in a substance

describe how thermal energy can be transferred by convection

from a hotter region to a cooler one

describe how thermal energy can be transferred by radiation

through infrared radiation waves

explain the role of convection in everyday situations

heating a room with a radiator:

• the radiator heats the air around it

• the warm air becomes less dense and rises

• cooler air moves in to replace it, gets heated and rises too

• this cycle creates convection currents that spread warm air around the room

boiling water:

• when water in a pot is heated from the bottom, the water at the bottom gets hot and rises

• cooler water from the top sinks to the bottom to get heated

• this creates a convection current inside the post that evenly heats the water

explain how emission is related to surface temperature

the higher the temperature, the more radiation an object emits, and the shorter the wavelengths of the emitted radiation

explain how absorption is related to surface temperature

a surface that absorbs more radiation will generally get hotter and vice versa

explain ways of reducing unwanted energy transfer - insulation

using materials with low thermal conductivity, trapping air and reducing drafts, as well as utilising glazing, cavity wall insulation and loft insulation