ENERGY Flashcards
Different energy stores ( eight)
Thermal kinetic gravitational potential elastic potential chemical magnetic electrostatic nuclear
what is a system
a system is a single object or a group of objects
what happens when a system changes
when a system changes energy is transferred
what are closed systems
Closed systems are systems where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero
how is energy transferred mechanically
energy is transferred mechanically by a force doing work
how is energy transferred electrically
energy is transferred electrically by moving charges
how is energy transferred to and away from the kinetic energy store
anything that is moving has energy in its kinetic energy store. Energy is transferred to this store when an object speeds up and is transferred away when an object slows down
how does mass and speed affect kinetic energy
The greater its mass and the faster its going the more energy there will be in its kinetic energy store.
EQUATION FOR KINETIC ENERGY( include what they are measured in)
1/2mv2
energy- joules
mass-kg
speed-(m/s)2
what is required to lift an object in a gravitational field
work
how does height affect the gpe store
the higher the object is lifted, the more energy is transferred to this store.
what else affects the gpe store other than height
mass and the strength of the objects gravitational field
EQUATION FOR GRAVITATIONAL POTENTIAL ENRERGY( include what they are measured in)
gpe=mgh gpe- joules mass-kg gravitational field strength-n/kg height-metres
what energy do falling objects transfer
when something falls energy from its gravitational potential energy store is transferred to its kinetic energy store
the rule for when objects fall when there Is NO AIR RESISTANCE
Energy lost from the gpe store = energy gained in the kinetic energy store
Energy lost from the gpe store =
energy gained in the kinetic energy store
how can energy be transferred to the elastic potential energy store
Stretching or squashing an object can transfer energy to its elastic potential energy store
EQUATION FOR ELASTIC POTENTIAL ENERGY
E=1/2ke2
elastic potential energy-joules
spring constant- (n/m)
extension- metres
DEFINITION SPECIFIC HEAT CAPACITY
Is the amount of energy needed to raise the temperature of 1kg of a substance by 1 degree
EQUATION FOR SPECIFIC HEAT CAPACITY
change in thermal energy=mass x specific heat capacity x temperature change change in thermal energy- joules mass-kg shc- j/kg temperature change- degrees
Energy can never be…..
DESTROYED
What is the conservation of energy
Energy can be transferred usefully, stored or dissipated but can never be created or destroyed
what happens to energy when its transferred between stores (useful and dissipated energy)
not all of the energy is transferred usefully into the store that you want it to go into. Some of the energy is always dissipated
energy transfer in a mobile phone
When you use the phone, energy is usefully transferred from the chemical energy store of the battery in the phone but some of this energy is dissipate to the thermal energy store of the phone.
What is power
is the rate of energy transfer or the rate of work
POWER EQUATIONS (with units)
P=E/T AND P=W/T
P- POWER
E-ENERGY TRANSFERRED
T-TIME
W-WORK DONE
WHAT IS CONDUCTION
Conduction is the process where vibrating particles transfer energy to neighbouring particles
where does conduction mainly happen in
happens mainly in solids
Describe how energy is transferred through a solid by heating (convection)
Heating transfers energy to the particles kinetic energy stores. These particles vibrate and transfer energy between them which gradually transfers energy through the solid.
what is thermal conductivity
thermal conductivity is how quickly energy is transferred through a material
materials with high thermal conductivity…
transfer energy between their particles quickly
WHAT IS CONVECTION
convection is where the energetic particles move away from hotter to cooler regions
where does convection mainly happen in
liquids and gases
how does convection happen in liquids and gases
energy is transferred by heating to the thermal store of the liquid or gas, this energy is shared across the kinetic energy store of the gas or liquids particles. When you heat a region of a gas or liquid, the particles move faster and the space between individual particles increases
because liquids can flow the warmer and less dense regions will rise above denser, cooler regions.
convection currents
radiators can create convection currents
1.energy is transferred from the radiator to nearby air particles by conduction
2.the air near the radiator becomes warmer and less dense
3.the warm air rises and is replaced by cooler air, the cooler hair is then heated by the radiator
4.at the same time the previously heated air transfers energy to the surroundings it cools, becomes denser and sinks
this repeats causing a flow of air to circulate around the room
ways to reduce unwanted energy transfers
lubrication and thermal insulation
what happens to energy during friction
whenever something moves there’s usually at least one frictional force acting against it, This causes energy in the system to be dissipated
how can you reduce friction from objects that are being rubbed together
lubricants eg-oil
what does insulation do
insulation reduces the rate of energy transfer by heating
How to prevent energy loss in a home (explain them)
- thick walls- the thicker the walls the lower their thermal conductivity and the lower the rate of energy transfer
- Cavity walls-air gap filled with foam reduces energy transfer by conduction. (inner and outer wall with air gap in the middle
- loft insulation- can reduce convection currents being created in lofts
- Double-Glazing- have an air gap between the two sheets of glass to prevent energy transfer by conduction
- Draught excluders- around doors and windows reduce energy transfer by convection
EFFICIENCY EQUATION
Useful output energy transfer/total input energy transfer
OR Useful power output/Total power input
