Extended_Electric_Power_Work_Energy_Presentation.pptx

Education

1. PAKISTAN INTERNATIONAL SCHOOL, JEDDAH CAMBRIDGE CURRICULUM SECTION (CCS) ACADEMIC YEAR (2024-2025) Day: Wednesday Date: 25 September 2024 Grade:10 Physics 0625 Week 8: Lesson 5 Unit:18

2. Chapter : 18 Electrical Quantities

3. Topic: 18.5 Electrical energy, work and power

4. Electric Power - Definition Electric power is the rate at which electrical energy is transferred by an electric circuit. It is measured in watts (W). Electric power is used in appliances such as heaters, motors, and light bulbs. It tells us how fast energy is being consumed or produced by the device.

5. Electric Power - Example Example: A 100W light bulb consumes 100 joules of energy every second. If it runs for 2 hours, the total energy consumed is 100W × 2 × 3600 = 720,000J (720 kJ).

6. Electric Power - Formula & Derivation The formula for electric power is P = IV , where P is power, I is current, and V is voltage. From Ohm's law (V = IR), we can derive: P = I × (IR), hence P = I²R . Alternatively, P = V²/R.

7. Work - Definition Work is the amount of energy transferred when a force moves an object over a distance. In electrical terms, work is done when a charge moves through a potential difference (voltage). In electrical circuits, work is done when electrical energy is transferred from one point to another, such as through a resistor or an appliance.

8. Work - Example Example: A 9V battery moves a charge of 2C through a circuit. The work done by the battery is: The formula for work is W = Q x V where W is work, Q is charge and V is voltage. W = 9V × 2C = 18 joules.

9. Energy - Definition Energy is the capacity to do work. Electrical energy is transferred when electric charges move through a conductor. Energy is measured in joules (J) or kilowatt-hours (kWh). Energy in electrical circuits is used in everyday appliances. The rate of energy consumption determines how much electricity an appliance uses over time.

10. Energy - Example Example: If a heater operates at 2kW for 3 hours, the energy consumed is 2kW × 3 hours = 6 kWh. This is equivalent to 6 × 3.6 × 10^6 joules (21.6 MJ).

11. Energy - Formula & Derivation The formula for energy is E = IVt , where E is energy, I is current, V is voltage, and t is time. This equation is derived from the fact that energy is the total work done over time: E = IVt .

12. Units of Electrical Energy In electrical circuits, energy is commonly measured in kilowatt-hours (kWh). 1 kWh = 1000 watts running for one hour. It is equivalent to 3.6 million joules (J). This is a more practical unit compared to joules, especially for measuring energy consumption in homes. For example, if a device with a power rating of 2 kW runs for 2 hours, it will consume 4 kWh of energy.

13. Home work Q no 27-34

14. Thank you