AQA GCSE PHYSICS - ENERGY
Energy is a fundamental concept in physics, governing the behavior of physical systems. Understanding energy stores, transfers, and conservation is crucial for problem-solving in physics and real-world applications. Below is a detailed breakdown of key energy topics in the AQA GCSE Physics curriculum, enriched with explanations, equations, and examples.
1. Energy Stores
Energy exists in different stores and can be transferred between them.
Types of Energy Stores
Kinetic Energy (KE) – Energy stored in moving objects.
Formula: KE = 1/2mv²
Example: A cyclist moving at 10 m/s has kinetic energy depending on their mass and speed.
Gravitational Potential Energy (GPE) – Energy stored in objects at a height due to gravity.
Formula: GPE = mgh
Example: A book on a shelf has more GPE than one on the floor.
Elastic Potential Energy (EPE) – Energy stored in stretched or compressed objects.
Formula: EPE = 1/2ke²
Example: A stretched rubber band stores elastic potential energy.
Thermal Energy – Energy due to an object's temperature and particle movement.
Example: Boiling water has more thermal energy than ice cubes.
Chemical Energy – Energy stored in chemical bonds of substances.
Example: Food, fuel, and batteries store chemical energy.
Magnetic Energy – Energy stored in magnetic fields due to the position of magnetic poles.
Example: Two magnets attracting or repelling each other.
Electrostatic Energy – Energy stored due to the attraction or repulsion between charged objects.
Example: Static electricity causing hair to stand up.
Nuclear Energy – Energy stored in atomic nuclei, released during nuclear reactions.
Example: The energy produced in nuclear power plants or the Sun.
2. Energy Transfers
Energy can be transferred between stores in four main ways:
Mechanically (by a force moving an object)
Example: Lifting a weight transfers chemical energy (muscles) to gravitational potential energy.
Electrically (via electric currents)
Example: A battery powers a lamp, converting chemical energy to electrical energy, then light and thermal energy.
By Heating (via conduction, convection, or radiation)
Example: A kettle transfers electrical energy to thermal energy in the water.
By Radiation (via light or sound waves)
Example: The Sun emits radiation that warms the Earth.
3. Conservation of Energy
Principle of Conservation of Energy:
Energy cannot be created or destroyed, only transferred between stores.
Total energy in a closed system remains constant, though some energy may be dissipated (spread out and become less useful).
Dissipation of Energy:
Often, energy is lost as heat due to friction or resistance.
Example: A moving car loses energy to air resistance and road friction as thermal energy.
Reducing Energy Waste:
Lubrication reduces friction (e.g., oiling machine parts).
Insulation reduces heat loss (e.g., double-glazed windows).
4. Work Done & Power
Work Done (W): The transfer of energy when a force moves an object.
Formula: W = Fd
Example: Pushing a shopping cart with a force of 50N over 2m does 100 Joules of work.
Power (P): The rate of energy transfer.
Formula: P=E/t
Example: A 100W light bulb transfers 100 Joules of energy per second.
5. Efficiency
Efficiency measures how much of the total energy input is usefully transferred.
Formula: Efficiency = (Useful Energy Output/Total Energy Input)×100%
Example:
An electric motor receives 200J but only transfers 160J to kinetic energy.
Efficiency = 160/200×100%=80%
Improving Efficiency:
Reducing friction (using lubricants).
Using thermal insulation (prevent heat loss).
Using energy-efficient appliances (LED lights instead of traditional bulbs).
6. Specific Heat Capacity (SHC)
The amount of energy needed to raise 1 kg of a substance by 1°C.
Formula:
Q=mcΔT
where:Q = energy transferred (Joules)
m = mass (kg)
c = specific heat capacity (J/kg°C)
ΔT = temperature change (°C)
Example:
Water has a high specific heat capacity (4200 J/kg°C), meaning it takes a lot of energy to heat up, making it useful in radiators.
7. Energy Resources
Renewable Energy Sources (Can be replenished)
Solar Power: Converts sunlight into electricity.
Example: Solar panels on rooftops generate power for homes.
Wind Power: Uses wind turbines to produce electricity.
Example: Wind farms in Germany and the UK supply renewable energy.
Hydroelectric Power (HEP): Water flow generates electricity.
Example: The Hoover Dam generates hydroelectric power.
Geothermal Energy: Uses heat from underground.
Example: Iceland uses geothermal energy for heating homes.
Biomass Energy: Organic materials burned for energy.
Example: Wood, waste, or biofuels used in power stations.
Non-Renewable Energy Sources (Finite supply)
Fossil Fuels (Coal, Oil, Gas):
Burned for energy but produces greenhouse gases.
Example: Power plants use coal to generate electricity.
Nuclear Power:
Uses uranium/plutonium for energy, high efficiency but produces radioactive waste.
Example: Nuclear power plants provide a stable energy supply.
Comparison of Energy Sources
8. National Grid & Energy Transfer
The National Grid distributes electricity efficiently.
Transformers reduce energy loss:
Step-up Transformers increase voltage for efficient long-distance transmission.
Step-down Transformers decrease voltage for safe home usage.
Example:
Power stations generate electricity → Step-up transformer increases voltage → High-voltage transmission → Step-down transformer reduces voltage for safe home use.