Science Half Yearly Yr 9
暂无描述。系统推荐的高质量记忆内容，适合每天坚持背诵学习。
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What does the law of conservation of energy state?
Energy cannot be created or destroyed; it can only be transferred or transformed from one form to another.
Provide an example of energy transfer.
The kinetic energy in a foot is transferred into kinetic energy in a ball.
Provide an example of energy transformation.
Gravitational potential energy in a roller coaster is transformed into kinetic energy.
Define energy efficiency.
Energy efficiency is how much usable energy is produced compared to the energy supplied.
How is energy efficiency described in terms of input and output?
Energy efficiency is the amount of useful energy output compared to the energy input.
Calculate the energy efficiency of a laptop if it produces sound, light, and heat.
Energy efficiency = useful energy output / total energy input x 100.
Identify common sources of energy loss.
• Heat • Friction
Describe a practical method to improve energy efficiency.
Using insulation to prevent heat loss.
Name various renewable energy sources.
• Solar • Wind • Geothermal • Wave
Name various non-renewable energy sources.
• Coal • Crude oil • Natural gas
What are the advantages of fossil fuels?
• Available on a large scale • Cheap to obtain • Energy-dense
What are the disadvantages of fossil fuels?
• Produce pollution and greenhouse gases • Contribute to global warming • Damages habitats
How is nuclear energy produced?
By splitting atoms using a process called nuclear fission.
What is the energy conversion process in nuclear energy?
Nuclear to thermal to electrical.
What are the advantages of nuclear energy?
• Large amount of energy from a small amount of fuel • No greenhouse gases produced • Very reliable
What are the disadvantages of nuclear energy?
• Produces radioactive waste • Expensive to build and remove • Risk of nuclear explosion
Describe how hydroelectric power stations generate electricity.
Water stored in dams at high elevations is released, converting gravitational potential energy to kinetic energy.
What are the advantages of wind energy?
• Does not produce emissions • Renewable • Free
What are the disadvantages of wind energy?
• Requires wind • Costly to make turbines • May cause aesthetic and noise pollution
What is Ohm’s Law?
V = IR, where voltage (V) is equal to current (I) multiplied by resistance (R).
Define current.
The flow of electric charge through a circuit.
Define resistance.
The opposition to the flow of electric current in a circuit.
What factors affect resistance?
• Material • Length • Thickness of a conductor
What is the relationship between voltage, current, and resistance?
For a constant current, voltage varies directly with resistance.