Summary Notes: Topic 1 Energy - AQA Physics GCSE

Energy Stores

• A system: an object or group of objects.
• Energy storage changes as system changes.

Examples

• Ball rolling and hitting a wall
  • System: Moving ball
  • Energy transfer: Kinetic energy to sound when hitting the wall.
• Vehicle slowing down
  • System: Moving vehicle
  • Energy transfer: Kinetic energy to thermal energy due to friction.

Calculating Energy

Kinetic Energy

• Formula: ( E_k = \frac{1}{2}mv^2 )
  • ( m ): mass in kilograms (kg)
  • ( v ): speed in metres per second (m/s)

Elastic Potential Energy

• Stored in a stretched spring.
• Formula: ( E_e = \frac{1}{2}ke^2 )
  • ( k ): spring constant in N/m
  • ( e ): extension in metres (m)

Gravitational Potential Energy

• Formula: ( E_p = mgh )
  • ( g ): gravitational field strength (9.8 m/s²)
  • ( h ): height in metres (m)

Specific Heat Capacity

• Energy required to raise temperature of 1kg by 1°C or 1K.
• Formula: ( \Delta E = mc\Delta T )
  • ( \Delta E ): change in thermal energy in joules (J)
  • ( c ): specific heat capacity in J/kg°C

Power

• Defined as the rate of energy transfer or rate of work done.
• Formula: ( P = \frac{E}{t} )
  • ( P ): power in watts (W)
  • ( E ): energy transferred in joules (J)
  • ( t ): time in seconds (s)
• 1 joule per second = 1 watt.
• More powerful motors transfer energy faster.

Energy Transfers

• Energy can be usefully transferred, stored, or dissipated but not created or destroyed.
• Dissipated energy is often wasted.

Reducing Energy Waste

• Lubrication: Reduces friction and heat loss.
• Thermal Insulation: Reduces loss of useful thermal energy.

Thermal Conductivity

• High thermal conductivity allows heat to travel easily.
• Low rate of cooling if walls are thick and have low thermal conductivity.

Efficiency

• Efficiency: Ratio of useful work done to energy supplied.
• Formula: ( \text{efficiency} = \frac{\text{useful energy output}}{\text{total energy input}} )
• Increase efficiency by reducing waste or recycling waste.

Energy Resources

Main Energy Sources

• Non-renewable: Fossil fuels, nuclear fuel.
• Renewable: Biofuel, wind, hydro-electricity, geothermal, tidal, solar, water waves.

Renewable vs Non-Renewable

• Renewable energy can be replenished (e.g., wind).
• Non-renewable provides large energy output but finite.
• Renewable energy development is rising due to fossil fuel limits.
• Renewable reliability issues: solar (weather/night), wind (intermittent).

Main Energy Uses

• Transport, electricity generation, heating.

Environmental Impact

• Extraction: Destruction of landscapes by fossil fuels; wind turbines visual impact.
• Use: Fossil fuels emit harmful gases; solar/wind have no emissions.

Patterns and Trends

• Fossil fuels rose during industrial revolution due to mining ease and high energy output.
• Renewables gain suitability as technology advances.
• Increasing energy demands vs. environmental issues.