Energy Changes in a System
Energy Changes in a System
Systems and Energy
- A system is an object or a group of objects.
- Systems can have energy stored in various ways. These ways include kinetic, thermal, gravitational potential, elastic potential, chemical, nuclear, and magnetic.
- Energy cannot be created or destroyed but only converted from one form to another. This is the principle of conservation of energy.
- Energy changes in a system can be calculated using the equation: change in energy = work done
Energy Transfers
- Energy transfers can occur by mechanisms such as heating or doing work.
- Energy can also be transferred between stores. For example, an object falling under gravity transfers energy from its gravitational potential energy store to its kinetic energy store.
- When energy is transferred between stores, some energy can be dissipated and spread into the surroundings, often as thermal energy.
Power
- The rate of energy transfer, or the rate of doing work, is measured as power.
- Power can be calculated using the equation: power = work done ÷ time
- The unit of power is the watt (W), where 1 W = 1 J/s.
Efficiency
- Efficiency is a measure of how much useful energy is transferred.
- The efficiency of an energy transfer can be calculated using the equation: efficiency = (useful power out ÷ total power in) x 100%
- No energy transfer is 100% efficient as some energy is always dissipated as wasted energy, usually in the form of heat.
- The goal for any system is to maximize the efficiency of the energy transfer.
Renewable and Non-renewable Energy Sources
- Energy sources can be classified as renewable and non-renewable.
- Renewable energy sources, such as wind and solar, are sustainable and will not run out.
- Non-renewable energy sources, like fossil fuels, are finite and will eventually run out.
- While renewable energies are more sustainable, there are issues with generating and storing sufficient power to meet demands.
- Non-renewable energies typically have larger environmental impacts, such as contributing to climate change through the release of carbon dioxide.