Energy Flashcards
What is the equation for gravitational potential energy?
GPE= mgh
Mass x Gravitational Field Strength x Height
What is the equation for kinetic energy?
½ mv²
½ x Mass x (Velocity)²
What is meant by the conservation of energy? ( 2 points)
● The total amount of energy in a closed system remains constant
● Energy cannot be made or destroyed but can change from one form to another
Describe the energy changes involved when a ball is thrown upwards and then returns to its starting position. Ignore air resistance.
● Upwards: KE is converted to GPE
● Peak: Maximum GPE, zero KE
● Downwards: GPE is converted to KE
State any changes in the total energy of a ball that is kicked, assuming that no external forces act.
The total energy of the system remains constant due to the conservation of energy.
Describe the energy changes that occur in a filament light-bulb.
● Electrical energy is transferred into light and heat energy
● Light is a useful energy form, heat is waste energy
Describe the energy transfers for a bungee jumper.
● When falling, the GPE is converted to KE of jumper
● As the cord tightens, KE is converted and stored as Elastic Potential Energy (EPE)
● At lowest point, the jumper’s initial GPE equals the EPE stored in the cord
Explain why a bungee jumper slows down once the cord begins to stretch.
● Kinetic energy decreases since it is converted to elastic potential energy
● Since KE is proportional to (velocity)²,
as KE decreases, so does velocity.
What is waste energy?
The energy that is not used by the device for its desired purpose, or not converted into the desired form.
State two equations to calculate efficiency.
=Useful Output Energy / Total Input Energy x100
=Useful Power Output/Total Power Output x100
State the consequence for energy transfer of a material with a high thermal conductivity.
The rate of energy transfer through the material is higher than for a material with a lower thermal conductivity.
Do double-glazed windows have a higher or lower thermal conductivity than single-glazed windows?
Lower, meaning less energy transfers through them.
State three methods of reducing heat loss in a building.
- Double glazing
- Loft and wall insulation
- Thicker walls
How can you reduce unwanted energy transfer in a mechanical system?
Reduce friction by lubricating moving parts.
e.g: bike chain
How can the efficiency of a system be increased?
- Reducing waste output
(by lubrication, thermal insulation etc.) - Recycling waste output
(eg. recycling thermal waste energy as input energy)
What is a renewable energy resource?
An energy source which can be replenished as it is being used up. (It never runs out)
Give four examples of renewable energy resources.
- Wind Energy
- Hydro-Electricity
- Tidal Energy
- Solar Energy
Give examples of a non-renewable energy resource.
Fossil Fuels (coal, natural gas, oil)
nuclear energy
What are the advantages of generating power using gas rather than coal?
● Flexible Generation: Gas power stations have short start-up times so can be switched on/off more readily
● Lower emissions of carbon dioxide
State two disadvantages of using renewable energy resources to generate power.
● Output often dependent on external factors (like wind speed), so supply is uncertain
● Renewable fuels often produce less energy per kg (so are less economical).
Explain the environmental impacts of burning fossil fuels.
● Carbon Dioxide contributes to the greenhouse effect, and causes global
warming
● Sulphur Dioxide leads to acid rain, which can damage buildings and crops
State three advantages of fossil fuels as an energy resource.
- Reliable: Not dependent on external factors so can generate power anytime
- Produce large amounts of energy per kg
- Still relatively abundant, so cost-effective
State three advantages of nuclear power.
- Very large amounts of energy per kg of fuel
- No greenhouse gases released, so doesn’t contribute to climate change
- Low fuel costs
Give examples of social factors to consider in energy production.
● Visual Pollution
● Sound Pollution
(in wind farms)
State three disadvantages of nuclear power.
- Produces nuclear waste:
harmful to humans & must be safely stored
for centuries. - It is a Non-Renewable energy source
- Risk of nuclear accidents:
fatal consequences on humans and the
environment
What are some disadvantages of using biofuels?
● When plants are burned/decay they release CO2
● In order to grow biofuels, you need to destroy land:
○ Habitat destruction
○ CO2 released when plants are cleared (for example, if they are burned)
● Growing biofuels reduces the land available for food crops
How does hydroelectric power produce energy?
● Rainwater collects behind a dam
● When this water is released, it is used
to turn a turbine
● This turbine turns a generator which produces electricity
What are the advantages of tidal energy sources?
● No greenhouse gases
● Fairly reliable - tides occur twice a day
● Cheap to run as tides are natural, so
free
What are the disadvantages of hydroelectric power?
● The dam may cause flooding
● It can cost a lot to install the required
infrastructure
What are some advantages of solar panels?●
● They don’t cause harm to the
environment
● They are a renewable resource
● They can be used in remote areas where other types of energy are less accessible
