Topic 1 - Energy Flashcards
What are the 8 energy stores that you need to know?
- Thermal energy stores
- Kineic energy stores
- Gravitational potential energy stores
- Elastic potential energy stores
- Chemical energy stores
- Magnetic energy stores
- Electrostatic energy stores
- Nuclear energy stores
Define
closed system.
a system in which neither matter nor energy can enter or leave
the net change in the total energy of a closed system is alway zero
What is the equation for
Kinetic Energy?
(involving mass, velocity and kinetic energy)
KE = 1/2(mv^2)
Kinetic Energy (J) = 1/2 (mass (kg) x speed (m/s)^2)
What is the equation for
Gravitational Potential Energy?
(involving field strength, height, mass and gpe)
GPE = mgh
GPE (J) = mass (kg) x gravitational field strength (N/kg) x height (m)
What is the equation for
Elastic Potential Energy?
(involving spring constant, extension and epe)
EPE = 1/2 (ke^2)
EPE (J) = 1/2 (spring constant (N/m) x extension (m)^2)
Define
specific heat capacity.
the amount of energy needed to raise the temperature of 1kg of a substance by 1°C
What equation links
specific heat capacity, energy transferred, mass and temperature?
ΔE = mcΔT
Change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg°C) x temperature change (°C)
What is the
conservation of energy principle?
energy can be transferred usefully, stored or dissipated, but can never be created or destroyed
What is
power?
And what is it measured in?
the rate of energy transfer or the rate of doing work
it is measured in watts
1 watt = 1 joule of energy transferred per second
What equation links
energy, power and time?
P = E/t
Power (W) = Energy transferred (J) / time (s)
What equation links
time, power and work done?
P = W/t
Power (W) = Work done (J) / time (s)
Define
conduction.
the process where vibrating particles transfer energy to neighbouring particles
(this occurs mainly in solids because liquids and gases are much more free to move around)
Define
thermal conductivity.
a measure of how quickly energy is transferred through a material by conduction
Define
convection.
the movement of high energy particles from warmer to cooler regions
(this only occurs in liquids and gases because the particles aren’t able to move in solids)
Describe how a
radiator creates convection currents.
(6 steps)
- Energy is transferred from the radiator to the nearby air particles by conduction (the air particles collide with the radiator surface).
- The air by the radiator becomes warmer and less dense.
- This warm air rises and is replaced by cooler air.
- The cooler air is then heated by the radiator.
- At the same time, the previously heated air transfers energy to the surroundings. It thus cools, becomes denser and sinks.
- This cycle repeats, causing a flow of air to circulate around the room - this is a convection current.
What does a
lubricant do?
reduces the friction between objects’ surfaces when they move
(these are usually liquids (like oil), so that they can flow easily between objects and coat them)
What are some things you can do to
prevent energy losses from heating in a house?
(2 things)
- have thick walls that are made from a material with a low thermal conductivity
- use thermal insulation
What are some examples of
thermal insulation?
(4)
- cavity walls
- loft insulation
- double-glazed windows
- draught excluders
What are
cavity walls?
and how do they work as thermal insulation?
an inner and an outer wall with an air gap in the middle
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the air gap reduces the amount of energy transferred by conduction through the walls
cavity wall insulation (where the cavity wall air gap is filled with foam), can also reduce energy transfer by convection in the wall cavity