P1,P2,P3- Energy Flashcards
What is efficiency
Useful energy transferred by a device devided by total energy supplied
What is a system
An object or group of objects, for example an apple sitting on a table is a system
What does defining a system help doing
It helps focus only on what is relevant to the situation being observed
What happens when a system is an equillibirum
equillibrium is a state in which opposing forces or influences are balanced so nothing changes
What is the meaning of equilibrium
A state where opposing forces are balanced
What is energy measured in
Joules (J)
What is a thermodynamic system
A system not limited from the surroundings by real of fake boundaries
What does an open system allow to happen
Allows the exchange of energy and matter to or from its surroundings
What does a closed system allow to happen
Allows the exchange of energy but not matter to or from its surroundings
What does an isolated system not allow happen
Does not allow the transfer of matter or energy to or from its surroundings
Describe the energy transfer when an object is thrown up
. The person holding the ball has energy in the chemical store
. When the ball is thrown, energy is transferred to the kenetic store
. When the ball is moving energy is transferred to gravitational/ potential store
Describe the energy transfer in a boiling kettle
When water is being boiled energy from the electricsl working store is transferred to the thermal store
What is kinetic energy
Kinetic energy is the energy of motion
How csn kinetic energy be calculated
Kenetic Energy (J) = 1/2 x m x v^2
What is gravitational potential energy
The energy of an object has due to its height in a gravitational field
How can gravitational energy be calculated
Gravitational potential energy (J)= m x g x h
What is the gravitational field strength of the earth
9.8 (N/Kg)
What is elastic potential energy
The energy stored in an elastic object when work is done on the object
How do you calculate elastic potential energy
1/2 x spring constant (K) x extension (E^2)
What is thermal energy
The energy contained within a system that is responsible for its temperature
How can thermal enegry be calculated
Mass(m) x specific heat capacity(c) x change in temperature
What is specific heat capacity of a substance
The amount of energy required to raise the temperature of 1kg of a substance by 1*
What does it mean if a substance has a low specific heat capacity
It takes less energy to change its temperature
What does it mean if a substance has a high specific heat capacity
It takes more energy to change its temperature
What the purpose of knowing the specific heat capacity of a substance
It determines how useful the substance would be for a specific purpose
What are the variables in the specific heat capacity practical
Independant variable= time
Dependant variable= temperature
Control variable= material of block, current supplied
What equipment is needed in the specific heat capacity practical
Block of metal, ammetre, voltmetre, thermometre, immersion heater, power supply, stopwatch
What is the 6 steps of the specific heat capcity practical
Assemble the apparatus by placing the heater into the top of the block
Measure the initial temperature of the block using the thermometre
Turn on the power and start the stopwatch
Take periodic measurements every 1 min of the voltage and the current from the voltmetre and ammetre
Switch off power supply, stop stopwatch and let apporetus cool
Monitor the themometer and record final temperature
What is a systematic error that could happen in the specific heat capacity practical
Zero error - reading thermometre wrong
Give one way to prevent random error in this practical
Make sure temperature value is read at eye leval to avoid parallat error
What is mechanical work
A force that acts over a distance. For example a person pushing a box across a floor
What is power
The rate of which work is done
How do you calculate power
Energy(j)/time(t)
What is the power,energy,time formula triangle and how do you use it
———-Energy(j)————Cover up the quantity you are calculating. If the other two are on the same
Power(p)——–Time(t) Multiply themand if one is above another you should devide top one by
bottom one
What is the law of coservation of energy
Energy cant be created or destroyed it can only be transferred from one to another
What is useful energy
Energy that is transferred from store to store and used for an intended purpose
What is wasted energy
Energy that is not useful for the intended purpose and is dissipated to its surroundings
What is thermal conduction
Thermal conduction is the diffusion of thermal energy (heat) within one or between multiple materials
What does the thermal conductivity of a material determine
The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material
Give 3 examples of substances with high thermal conductivity
Diamond
Aluminium
Graphite
what are the 8 energy stores
thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear
what are the 4 ways energy can be transferred
mechanically (a force doing work)
electrically (moving charges)
heating (light or sound)
radiation (light or sound)
what is a system
an object or a group of objects
what are closed systems
where neither matter or energy can enter or leave
what is the net change in the total energy of a closed system
0
what is work done
the amount of energy transferred
describe the energy transfer when a person throws a ball upwards
the initial force exerted by a person to throw a ball upwards does work. it causes an energy transfer from the chemical store of the persons arm to the kinetic store of the ball and arm
describe the energy transfer when a ball is dropped from a height
a ball dropped from a height is accelerated by gravity. the gravitational force does work causing energy to be transferred from the balls gravitational potential energy store to its kinetic energy store
describe the energy transfer when a car breaks after accelerating
the friction between a cars breaks and its wheels does work as it slows down causing an energy transfer from the wheels kinetic energy store to the thermal energy store of the surroundings
describe the specific heat capacity practical
have a block of the desired material you will be measuring and have two small wholes in the roof. measure the mass of block then wrap it in an insulating layer to reduce energy transferred to surroundings. insert themometre in one of the wholes and connect power supply to heater. measure the initial temperature of the block. turn on powwer supply and start stopwatch. as the block heats up take readings of the temperature and current every minute for 10 minutes then turn of power supply
what happens when you turn the power on in the specific heat capacity practical
the current in the circuit does work on the heater transferring energy electrically from the power supply to the heaters thermal energy store. this energy is then transferred to the materials thermal energy store by heating causing the materials temperature to increase
what happens to the current when the temperature of the material increaseses in the specific heat capacity practical
the current doesnt change
what is the conservation of energy principle
energy can be transferred, stored or dissipated but can never be created or destroyed
what is dissipated energy
wasted energy- energy that isnt being used efficiently and not useful
what are the two main ways to reduce amount of energy wasted
lubrication and thermal insulation
how does lubrication reduce energy loss
whenevr somethnig moves theres usually one frictional force acting against it causing some energy in the system to be dissipated. lubricants can be used to reduce friction between the objects
what is conduction
how thermal energy traves through solids
what does it mean if a mateiral has a high thermal condutcivity
they can transfer thermal energy betweeen their particles at a faster rate
how does insulation help reduce energy dissipated
an insulator will keep the heat in the desired area so no thermal energy is dissipated to the surroundings
what determines how efficient a device is
by the amount of energy ‘wasted’. an efficient device is one which transfers energy from one place to another without wasting a lot of energy
what are the three main 3 fossil fuels
coal, oil and natural gas
what is one way vehicles can function with renewable energy resources.
vehicles that run on pure bio-fules is renewable
what are two renewable energy sources that can be used for heating instead of using natural gas
a geothermal heat pump
solar water heaters work by using the sun to heat water which is then pumped into radiators in the building
give three positives of wind turbines
theres no pollution when the turbines are working
theres no permanent damage to the landscape - if you want to remove the turbines the view will just return to normal
there are no fuel costs and minimal running costs
give three negatives of windturbines
they are very noisy which can disturb people living close by
they dont generate any energy when the wind stops and on average wind turbines only produce electricity 70-85% of the time
the initial costs are quite high
give three positives of solar cells that are put on houses
theres no pollution once applied to area
in sunny countries solar energy is a very reliable source of energy, but only in the day time and can still be cost - effective in cloudy countries too
after making the energy is free and running costs are almost 0
what are 3 negatives of solar cells that are put onto houses
it will only generate electricity in the day,
initial costs are high
usually used to generate electricity on a small scale
what is geothermal power
thermal energy from the earth
give 2 positives of geothermal energy
doe very little damage to the environment
very reliable
give two negatives of geothermal energy
they arent many suitable locations for these power plants
the cost of building a power plant is often high compares to the amount of energy it produces
Why cant a device be more than 100% efficient
Because the device cant create energy
What is dependent variable
The variable you measure
What is independent variable
Variable you change
What is the control variable
The variable you keep the same
What is zero error
Any indication that a measuring system gives a false reading when the true value of a measured quantity is zero
What is random error
A measurement error due to unpredictable variation from one reading to the next
What is a measurement error
A difference between a measured value and the true value
