# Energy Transfers

## Energy Transfers

### Basic Law of Energy Transfer

• Energy cannot be created or destroyed. This is better known as the law of conservation of energy.
• Despite not being able to create or destroy energy, it can be transferred or transformed from one form into another.
• For instance, in a torch, chemical energy stored in the batteries is transformed into light and thermal energy.

### Types of Energy Transfers

• Mechanical work: A force acting on an object moves the object, transferring energy in the process. For instance, pushing a trolley imparts kinetic energy to it.
• Electrical work: Energy can be transferred via an electric current, such as when a fan uses electricity to generate wind.
• Heating: Energy can be transferred from a hotter object to a cooler one, increasing the cooler object’s internal energy.
• Radiation: Energy can be transferred via light or other electromagnetic waves, such as the energy received from the sun.

### Energy Efficiency

• Efficiency measures how much of the input energy is usefully transferred and not wasted. The higher the percentage, the more efficient the energy transfer.
• Efficiency can be calculated using the formula: Efficiency = (Useful energy output / Total energy input) × 100%.
• All energy transfers are to some extent inefficient as some energy is invariably ‘wasted’, most commonly as thermal energy or heat.
• Efficiency improvements are vital for sustainable energy use, reducing the amount of energy required for a given task, and limiting environmental damage.

### Energy in Practical Applications

• For example, in a car, chemical energy in petrol is transformed into kinetic energy of the moving vehicle, but also non-useful forms such as sound and heat.
• In a coal-burning power station, energy transfers occur successively: chemical (coal) to thermal (heat) to kinetic (steam) to mechanical (turbine) to electrical (generator).
• Many appliances including TVs, computers and fridges use electrical energy and convert it into other forms - thermal, light, sound etc.
• Knowledge about these practical applications of energy transfer is crucial when answering real-life scenario based questions.
• The key is to identify all instances where energy is usefully converted or lost as waste energy.