Energy Flashcards
Define energy
Ability to do work (Joules)
Define work done
Energy transferred (Joules)
Explain what a system is
An object or group of objects
Describe the energy changes when a ball is thrown upwards.
Chemical store of hand – Kinetic store of ball– Potential store of ball– Kinetic of ball
Describe the energy changes when a moving object hits an obstacle.
Kinetic store of moving object– thermal store of obstacle
Describe the energy changes for a vehicle slowing down.
Opposite force (of deceleration) causes accelerating object to slow down. Kinetic store – thermal energy store of surrounding (due to friction)
If a system is ‘open’ what can be exchanged with the outside environment?
Matter and energy
If a system is ‘closed’ what can be exchanged with the outside environment?
Energy
If a system is ‘isolated’ what can be exchanged with the outside environment?
Nothing
Name the 8 energy stores.
Thermal, nuclear, kinetic, gravitational potential, elastic, chemical, magnetic and electrostatic
Explain kinetic energy stores.
Energy possessed by moving objects
Explain gravitational potential energy stores.
The energy stored in an object due to height.
Explain thermal energy stores.
Energy possessed by hot objects in which particles move faster.
Explain elastic energy stores.
Energy stored in stretched or compressed objects.
Explain nuclear energy stores.
The energy stored in the nucleus of atoms, released in nuclear reactions.
Explain chemical energy stores.
The energy stored in the bonds of chemical compounds, such as food, fuel, or batteries.
Explain electrostatic energy stores.
The energy stored in objects due to the interaction of electrically charged particles.
Explain magnetic energy stores.
The energy stored in magnetic fields, which can exert forces on magnetic materials.
What are the energy transfer pathways?
Mechanic, electric, heating by particles and heating by radiation.
Explain the mechanical energy pathway.
When a force acts on an object: stretching/pushing/pulling.
Explain the electrical energy pathway.
Electrons carrying a current through a wire will also carry energy.
Explain heating by particles as an energy transfer pathway.
When particles move faster, they collide with other particles to transfer energy until the entire substance reaches a uniform temperature.
Explain heating by radiation as an energy transfer pathway.
When energy is transferred by electromagnetic waves.
What is the formula for kinetic energy?
1/2 x mass x velocity^2
What happens to kinetic energy in accelerating objects?
Energy in kinetic store increases (speed increasing)
What happens to kinetic energy in decelerating objects?
energy transferred away from kinetic store
What is the formula for gravitational potential energy?
mass x gravitational field strength x height
What is gravitational field strength?
Force that exists around every mass, its dependent on the mass of an object.
What is the formula of elastic potential energy?
1/2 x spring constant x extention^2
Define specific heat capacity.
The amount of energy needed to raise the temperature of 1 kg of a substance by 1 degree celsius.
What is the formula for specific heat capacity?
mass x SHC x temp change = energy change
RP1: How do we find the SHC of a substance?
Method: Place immersion heater into substance + connect to joulemeter.
Fully insulate.
Measure start temp.
Turn on power supply.
Wait 30 mins.
Turn off supply and record final temp.
Use formula to calc.
Define power.
The rate at which work is done/energy is transferred.
Give the two formulas for power.
P= E/t
p=W/t
Give the law of the conservation/dissipation of energy.
Energy cannot be created or destroyed, only transferred between stores.
What 3 things does the law of conservation/dissipation of energy mean?
-Total energy in an isolated system remains constant
-Energy can be transferred usefully to do work
-Energy can be dissipated to the thermal energy stores of the surroundings
Describe how energy is transferred when a ball hits a bat.
Bat moves and has kinetic energy, which is transferred to kinetic energy store of the ball, some energy is dissipated by heating to the thermal stores.
What are less useful energy transfer examples?
Heat, light and sound
What is meant by useful and wasted energy?
Useful: Energy transferred from stores for its intended purpose
Wasted: Energy not used for its intended purpose being dissipated into its surroundings
What are two methods of reducing energy loss?
Lubrication: Reduces friction
Insulation: Reducing heat
What effects the insulation of heat in homes?
Thickness of walls (heat doesn’t pass) and thermal conductivity (high conductivity) + sealing close so air doesn’t pass for convection.
Define efficiency.
A measure of the amount of wasted energy in an energy transfer.
What causes inefficiency in energy transfers?
Friction between moving parts, air resistance (friction in air), electrical resistance, sound.
all transfer by heat
How do we reduce friction, air resistance, electrical resistance and sound?
Friction: Lubricate parts
Air resistance: Streamline
Electrical resistance: reduce current/resistance
Sound: Lubricate parts
What is an energy resource?
Large stores of energy that can be used to generate electricity and heat homes.
How are water waves and tidal energy generated?
Moves the kinetic energy is waves to kinetic store of turbines, then kinetic store of the generator to transfer energy electrically to the National Grid.
How is hydro-electricity generated?
Water is stored in reservoirs at height, so when released, rushing water turns turbines.
How are fossil fuels used to generate energy?
Fossil fuels are combusted to heat water into steam which turns the turbines in the generator.
How is geothermal energy generated for electricity?
Hot rocks underground boil water to produce steam, which turn turbines to generate electricity.
How is nuclear energy produced and used for producing electricity?
Nuclear fuels react to heat water to turn turbines with steam, to generate electricity.
How are biofuels used to produce energy for electricity?
Plant matter, ethanol and methane being burned rather than fossil fuels to heat water to produce steam and move turbines and generators for electricity.
How is solar power used to generate energy for electricty?
Solar cells turn light into electricity and solar panels use thermal radiation to heat water to produce warm water.
How is wind used to generate electricity?
Turns turbines directly for electricity,
Give the advantages/disadvantage of each of the energy sources.
Fossil fuels: Reliable but pollution.
Biofuels: Less emissions but land needed.
Nuclear: Large amounts of energy but radioactive.
Wind: No pollution but unreliable.
Hydroelectric: No pollution but can flood areas.
Geothermal: Reliable + small stations but harmful gases underground.
Solar: No pollution but only works in sun.
Tidal: No pollution but destroys habitats.
Explain the greenhouse effect.
The Sun’s rays are emitted back into space but some thermal energy is absorbed by greenhouse gases in the atmosphere and so the Earth becomes hotter.
