Physics - EDEXCEL IGCSE - Energy Resources and Transfer

Section 4 - Energy resources and transfer:

Examples of energy transfer:

• Chemical energy (in food) —> Kinetic energy (in muscles)
• Electrical energy (in circuits) —> Heat energy (from heat leakage from excess current)
• Kinetic energy (in muscles) —> Sound energy (from voice box)
• Elastic potential energy (in taught string) —> Kinetic energy (when string is relaxed)
• Chemical energy (battery) —> Light energy (from phone screen)

Energy is never lost but transferred, this is the principle of conservation of energy.

Energy Efficiency:

Energy efficiency = useful energy output / total energy input

The energy efficiency can be shown by using a Sankey diagram as below: 

The above Sankey diagram shows a light bulb. Its energy efficiency is 0.1 as it loses most of its energy through heat.

Energy can be transferred through conduction (transferred through touch), radiation (infrared) and convection whereby particles with energy rise allowing others to fill the space. If the source of energy continues the convection will continue and repeat. Convection is responsible for the distribution of heat energy. An insulator is bad at conducting so insulating buildings will stop heat energy from conducting away.

W = f * d

work done = force * distance moved in the direction of the force

Work done is also equal to energy transferred.

GPE = m * g * h

gravitational potential energy = mass * gravity field strength * height

KE = 0.5 * m * v²

kinetic energy = 0.5 * mass * velocity * velocity

p = W / t

power = work done / time taken

Energy production:

The following three methods all use natural processes to generate energy. The advantage with this is that it is green and renewable. However, they produce generally less energy and also cause visual pollution 

• wind —> turns turbine —> runs generator —> creates electrical energy
• water —> turns turbine —> runs generator —> creates electrical energy
• geothermal reserves —> heats water to make steam —> turns turbine —> runs generator —> creates electrical energy

The next two methods also use natural processes. However, these two rely on the weather. They again produce relatively less energy and can cause visual pollution 

• solar heating system —> heats water to make steam —> turns turbine —> runs generator —> creates electrical energy
• solar cells —> converter changes sunlight into electricity—> creates electrical energy

The next is probably the most common method of production energy. However, it causes pollution and is non-renewable. It does produce relatively more energy, though.

• fossil fuels —> heats water to make steam —> turns turbine —> runs generator —> creates electrical energy

This final one is probably the most dangerous method and produces toxic nuclear waste. However, it produces large amounts of energy and is technically renewable.

• uranium —> nuclear fission —> heats water to make steam —> turns turbine —> runs generator —> creates electrical energy