Electricity Generation, Transmission, and Distribution | Grade 9 Science Quarter 4 Week 8

Key Concepts:

• Electricity Generation: Producing electrical energy from various sources (geothermal, running water, wind, solar, nuclear, fossil fuels).
• Geothermal Power Plant: Uses heat from within the Earth (300-700°F) to produce electricity.
• Generator: A device that converts mechanical energy into electrical energy through electromagnetic induction.
• Electromagnetic Induction: The phenomenon discovered by Michael Faraday where a changing magnetic field induces an electric current in a conductor.
• Step-Up Transformer: Increases voltage for efficient long-distance transmission (up to 756 kV).
• Step-Down Transformer: Decreases voltage for distribution to substations (13 kV to 2 kV) and homes (240 V and 120 V).
• Power Consumption: The amount of electrical power used, measured in watts (W) or kilowatts (kW).
• Energy Consumption: The total amount of electrical energy used over time, measured in kilowatt-hours (kWh).
• Turbine: A rotating shaft with blades that is turned by a source of energy (e.g., steam, water) to drive a generator.
• Transmission Lines: Power cables that carry high-voltage electricity over long distances.
• Distribution Lines: Carries electricity at lower voltage and is used to distribute power to end consumers.

1. Electricity Generation

• Electrical energy is vital in the modern age and is produced from various sources.
• Industries and homes benefit from electricity through appliances, gadgets, lights, and alarm systems.
• Electricity generation involves three processes: generation, transmission, and distribution.
• Power plants generate electricity from different energy sources.
• Geothermal Power Plant: Uses heat from within the earth (300-700°F) by drilling wells and piping steam or hot water to the surface. The steam drives turbines connected to generators. Cooled steam is condensed and injected back into the ground.
• Other sources include running water, wind, light, heat from the sun, nuclear reactions, and burning fossil fuels.
• The Philippines is exploring viable, non-conventional energy resources.

2. Generation and Magnetism

• Electricity is generated by turning large turbines connected to a generator.
• Generator: Converts mechanical energy to electrical energy through the interaction between a changing magnetic field and a conductor.
• A magnet or conductor at rest cannot produce electric current.
• Electromagnetic Induction: Discovered by Michael Faraday, current is induced by moving the magnet or the conductor.

3. Transmission and Distribution

• After generation, electricity flows through large wires to a step-up transformer.
• Step-Up Transformer: Raises the voltage as high as 756 kilovolts (kV) for long-distance transmission.
• The electric current travels through transmission power lines to substations.
• At substations, a step-down transformer lowers the voltage to between 13 kV and 2 kV.
• From substations, electricity is sent to pole transformers or transformer boxes.
• Step-Down Transformer: Lowers the voltage again to between 240 volts and 120 volts for residential use.
• Electricity enters homes through a service box with an electric meter.
• Wires distribute electricity to lights and appliances.

4. Consumption and Computation

• Electric companies charge based on electrical energy used.
• The total energy used is calculated by multiplying power consumption by the duration of use.
• Formula: E = P x T, where:
  • E = Energy used (kilowatt-hour, kWh)
  • P = Power (watts, W)
  • T = Time (hours, h)
• The unit of measurement for energy used is kilowatt-hour (kWh), which is one kilowatt of power for one hour.

5. Sample Problem

• Problem: How much electrical energy is used by a 250-watt refrigerator for 8 hours if the cost of electricity is 8.32 pesos per kilowatt-hour? How much will the use of the refrigerator cost?
• Given:
  • Power (P) = 250 watts
  • Time (T) = 8 hours
  • Cost of electricity = 8.32 pesos per kWh
• Conversion:
  • Convert 250 watts to kilowatts: 250 watts / 1000 watts/kilowatt = 0.25 kilowatts
• Calculation:
  • Energy (E) = P x T = 0.25 kW x 8 hours = 2 kWh
  • Cost = Cost per kWh x Energy used = 8.32 pesos/kWh x 2 kWh = 16.64 pesos
• Answer: The refrigerator uses 2 kWh of energy, costing 16.64 pesos.

6. Key Concepts Summary

• Powerplant: A facility where electricity is generated from energy sources.
• Generator: Converts mechanical energy into electrical energy.
• Transmission Lines: Power cables that carry high voltage electricity over long distances.
• Distribution Lines: Carries electricity at lower voltage and is used to distribute power to end consumers.
• Basic equipment includes the turbine, generator, and transformer.
• Turbine: A rotating shaft with blades.
• Transformer: Increases or decreases voltage.
• Power loss occurs during transmission due to the resistance of wires.

7. Synthesis/Conclusion

The lesson explains the complete process of electricity, from generation at power plants using various energy sources, through transmission via high-voltage lines and transformers, to distribution to homes and businesses at lower voltages. It also covers how energy consumption is calculated and provides a practical example. The key takeaway is understanding the interconnectedness of these processes and the importance of efficient energy use.