Energy Stores and Transfers in Physics

Energy Stores

• There are eight different energy stores: kinetic, thermal, gravitational potential, elastic potential, chemical, electrostatic, magnetic, and nuclear.
• Kinetic energy is the energy of motion; it is higher when an object moves faster and/or has more mass.
• Thermal energy is the energy of a substance related to its temperature.
• Gravitational potential energy is the energy an object has due to its position in a gravitational field.
• Elastic potential energy is the energy stored within a stretched or compressed object.
• Chemical energy is the energy stored in the bonds of molecules, for example, in fuels.
• Electrostatic energy is the energy stored in a charged particle.
• Magnetic energy is the energy stored in a magnetic field.
• Nuclear energy is the energy stored in the nucleus of an atom.

Energy Transfers

• Three main ways energy can be transferred between stores:
  • Heating: Energy is transferred from a hotter object to a cooler object.
  • Work Done: Energy is transferred by a force acting over a distance.
  • Radiation: Energy is transferred via electromagnetic waves (e.g., light from the sun).
• Example: A tennis ball dropped from a height.
  • Initial state: Gravitational potential energy store.
  • Falling: As the ball falls, its gravitational potential energy converts into kinetic energy, and the ball gains speed.
  • Just before impact: Most of the energy is in the kinetic energy store.

Kinetic Energy

• Equation: E = 1/2mv²
  • E: Kinetic energy (measured in Joules, J)
  • m: Mass (measured in kilograms, kg)
  • v: Velocity (measured in meters per second, m/s)

Gravitational Potential Energy

• Equation: E = mgh
  • E: Gravitational potential energy (measured in Joules, J)
  • m: Mass (measured in kilograms, kg)
  • g: Gravitational field strength (measured in Newtons per kilogram, N/kg, or meters per second squared, m/s²)
  • h: Height (measured in meters, m)

Elastic Potential Energy

• Equation: E = 1/2kx²
  • E: Elastic potential energy (measured in Joules, J)
  • k: Spring constant (measured in Newtons per meter, N/m)
  • x: Extension or compression (measured in meters, m)

Specific Heat Capacity

• The energy required to increase the temperature of 1 kilogram of a substance by 1 degree Celsius.
• Equation: ΔE = mcΔT
  • ΔE: Change in thermal energy (measured in Joules, J)
  • m: Mass (measured in kilograms, kg)
  • c: Specific heat capacity (measured in Joules per kilogram per degree Celsius, J/kg°C)
  • ΔT: Change in temperature (measured in degrees Celsius, °C)

Conservation of Energy

• Energy cannot be created or destroyed, only transferred, stored, or dissipated.
• Implication: The total amount of energy in the universe is constant.

Power

• The rate at which work is done or energy is transferred.
• Equation: Power = Work done / Time taken
  • or Power = Energy transferred / Time taken
  • Power (measured in Watts, W)
  • Work done and Energy transferred (measured in Joules, J)
  • Time taken (measured in seconds, s)

Conduction

• Heat transfer through solids by vibration of particles.
• Explanation: Hot particles vibrate faster, transferring energy to neighboring particles, causing them to vibrate faster as well.

Convection

• Heat transfer through liquids and gases by movement of the fluid.
• Explanation: Warmer, less dense fluids rise, and cooler, denser fluids sink, creating cycles that distribute heat.

Efficiency

• The proportion of the total energy input that is converted into useful output energy.
• Equation: Efficiency = Useful energy output / Total energy input
  • Efficiency (usually expressed as a percentage)

Energy Resources

• Renewable: Energy sources that are constantly replenished naturally (e.g., solar, wind, hydroelectric, tidal, geothermal, biomass).
  • Pros: Renewable, less harmful to the environment.
  • Cons: Can be unreliable, expensive to build.
• Non-renewable: Energy sources that are finite and will eventually run out (e.g., fossil fuels (coal, oil, natural gas), nuclear).
  • Pros: Reliable, relatively inexpensive.
  • Cons: Will run out, harmful to the environment.

National Grid

• A system of power lines and transformers that carry electricity across a country.
• Purpose: Distribute electricity from power stations to homes and businesses efficiently.
  • Step-up Transformers: Increase voltage to reduce energy loss during transmission.
  • Pylons: Support high-voltage power lines.
  • Step-down Transformers: Decrease voltage to safe levels for use in homes and businesses.

This quiz covers the eight different energy stores, including kinetic, thermal, and chemical energy. It also explores the methods of energy transfer, such as heating and work done. Test your knowledge of these fundamental concepts in physics!