Energy Concepts
Basic Principles
- Energy is a concept, not a tangible object.
- Total energy in a system is always conserved; it cannot be created or destroyed.
- Energy can transform into mass (important for nuclear fission and fusion).
Types of Energy (Energy Stores)
- Kinetic Energy:
- Formula: (E_k = \frac{1}{2}mv^2)
- Dependent on mass (m) and velocity (v).
- Gravitational Potential Energy (GPE):
- Formula: (E_p = mgh)
- Dependent on mass (m), gravitational field strength (g, typically 9.8 or 10 N/kg), and height (h).
- Elastic Potential Energy:
- Formula: (E = \frac{1}{2}k e^2)
- Dependent on spring constant (k) and extension (e).
- Thermal Energy:
- Formula: (E = mc\Delta T)
- SHC (Specific Heat Capacity) is the energy needed to raise 1 kg of a substance by 1°C.
- Chemical Potential Energy: Present in food and fuels, no specific formula.
Energy Transfer
- Energy transfer is necessary for any process in a system.
- In a closed system, energy is not lost to or gained from the surroundings.
- Example: Roller coaster GPE converts to KE.
- At the top: High GPE, low KE.
- At the bottom: Low GPE, high KE.
Equation Rearrangement
- Focus on using symbols for rearranging equations.
- Example for speed: Rearrange kinetic energy equation for velocity (v).
- (v = \sqrt{\frac{2E_k}{m}})
Energy Loss and Efficiency
- Not all energy transformations are 100% efficient.
- Energy can be lost due to air resistance or friction, indicating an open system.
Specific Heat Capacity Practical
- Method to find SHC by heating materials and measuring temperature change.
- Issues: Heat loss to surroundings affects accuracy.
Power
- Definition: Rate of energy transfer.
- Formula: (P = \frac{E}{t})
- Measured in Watts (W), equivalent to Joules per second.
Efficiency
- Measure of how much input energy is used usefully.
- Formula: (\text{Efficiency} = \frac{\text{Useful Energy Output}}{\text{Total Energy Input}})
- Can be expressed as a decimal or percentage.
Energy Sources
- Non-renewable (Finite): Fossil fuels (coal, oil, gas), nuclear fuel.
- Renewable: Wind, hydroelectric, solar, geothermal, biofuel.
Practical Tips
- Insulation can reduce heat loss from buildings.
- Experiments can measure insulation effectiveness by using different materials.
Note: Practical experiments and specific calculations are important for deeper understanding and application.