Topic 1 - Energy Flashcards
name all of the energy stores you need to know:
thermal kinetic gravitational potential elastic potential chemical magnetic electrostatic nuclear
how is energy transferred?
mechanically
electrically
by heating or by radiation
how is energy transferred mechanically?
by a force doing work
how is energy transferred electrically?
work done by moving charges
how is energy transferred by heating or radiation?
e.g. light or sound
what is a system?
a word for a single object or group of objects that you’re interested in
what happens when a system changes?
energy is transferred
how can energy be transferred in a system?
into or away from the system
between different objects in the system
between different types of energy stores
what are closed systems?
systems where neither matter nor energy can enter or leave. the net change in the total energy of a closed system is always 0
how is energy transferred when boiling water in a kettle?
when the water is the system, energy is transferred to the water by heating into the waters thermal energy store
if the kettle and the water is a two object system, energy is transferred electrically to the thermal energy store of the kettle, which transfers to the waters thermal energy store by heating
whats another word for work done?
energy transferred
how can work be done?
when current flows or by a force moving an object
examples of work being done:
the initial force of someone throwing a ball upwards, kinetic -> gravitational
a ball dropping from a height, the gravitational force does work, gravitational -> kinetic
the friction between a cars breaks and its wheels kinetic -> thermal
what does anything moving have?
energy in its kinetic energy store. energy is transferred to this store when an object speeds up and away from it when it slows down.
what does the amount of energy in the kinetic energy store depend on?
the objects mass and speed. the greater the mass the faster it goes, the more kinetic energy
what is the formula for kinetic energy?
KE = 1/2mv²
what happens when an object is lifted in a gravitational field?
it requires work, this causes an energy transfer to the gravitational energy store. the higher the object the more energy in the GPE store
what does the amount of energy in the GPE store depend on?
the objects mass, its height and the strength of the gravitational field.
what is the equation for gravitational potential energy?
GPE = mgh
what energy transfers happen when an object falls?
energy is transferred from its gravitational energy store to its kinetic energy store. air resistance also transfers energy into other stores like thermal energy of the surroundings
what happens if something falls if there’s no air resistance ?
energy lost from GPE store = energy gained in the kinetic energy store
when will energy be transferred to the elastic potential store?
stretching or squashing an object
how can the energy in the elastic potential energy store be found?
EPE=1/2ke²
elastic potwntial energy= 1/2 x spring constant x extension²
what is specific heat capacity?
the amount of energy needed to raise the temperature of 1kg of a substance to 1*C
what is the equation that links SHC and energy transferred?
ΔE=mcΔθ
change in thermal energy = mass x SHC x change in temperature
how to investigate specific heat capacity of a solid object?
get a block of the material with 2 holes in it
measure it then wrap it in a insulating layer
insert heater and thermometer
measure initial temp then turn on power supply to 10V and start stop watch
take readings of temperature and current every minute for 10 minutes the current shouldn’t change
for an investigation on SHC why does the object need an insulating layer?
to reduce the energy transferred to the surroundings
how does the heater heat the block in a SHC investigation?
when the power supply is turned on the current in the circuit does work on the heater, transferring energy electrically to the heaters thermal energy store, this is then transferred to the materials thermal energy store, so its temperature increases
how can you work out the energy transferred to the heater at each interval in a SHC investigation?
use the current and potential difference to find power using P=IV
then use E=Pt to find the amount of energy transferred at each interval
how to find specific heat capacity from the results of a specific heat capacity graph?
assuming all the heat from the heater was transferred to the material, you can plot a graph of energy transferred by temperature.
the gradient is Δθ/ΔE
so the specific heat capacity = 1/(gradient x mass of material)
what is the conservation of energy principle?
energy can be transferred usefully, stored or dissipated, but never be created or destroyed
what is an example of energy being wasted?
in phones energy is usefully transferred from the chemical energy store of the battery but some is dissipated by transferring to thermal energy stores
example of energy transfers for a closed system:
cold spoon dropped into insulated flask of hot soup, which is then sealed. this forms a closed system
energy is transferred from thermal energy store of soup to useless thermal energy store of spoon. net change of energy is 0 but soup cools slightly
what is power?
the rate of energy transfer, or the rate of doing work. measured in watts
what equations can be used to find power?
P=E/t
P=W/t
what does increasing power do?
it doesn’t mean more energy is transferred at once but that the same amount of energy is transferred in less time
