Lecture Notes: Power and Energy of Electric Appliances

Introduction

• Focus on power and energy of electric appliances.
• Part of Grade 11 science textbook (Physics lesson).
• Importance of understanding electric appliances in everyday life: computers, phones, fans, cookers, etc.

Key Concepts

Electric Appliances

• Devices using current electricity in daily life.
• Convert electric energy into other energy forms (e.g., light, sound, heat).

Power and Energy

• Power: Rate of energy consumption or output of an appliance.
• Measured in watts (W).
• Examples: Light bulbs (13W, 20W, 40W, etc.).
• Energy: Total electric energy consumed depends on power and time of operation.

Energy Conversion Examples

• Fluorescent Light: Electricity to light.
• Television: Electricity to light and sound.
• Radio: Electricity to sound.
• Electric Oven/Microwave: Electricity to heat.
• Electric Motor: Electricity to kinetic energy.
• Induction Cooker: Electricity to heat via magnetic induction.

Efficiency of Electric Appliances

• Not 100% efficient due to resistance.
• Energy lost as heat due to internal resistance.

Important Equations

• Power (P): P = V * I (Voltage * Current)
• Energy (E): E = P * T (Power * Time)
• Alternate formula: E = V * I * T

Household Electric Circuits

• Components: Main switch, trip switch, bulbs, plug sockets, etc.
• Understanding how circuits operate in homes.

Energy Measurement

• Measured in kilowatt-hours as per household electric meters.

Example Calculations

• Power Calculation: Given voltage and current, calculate power.
• Energy Consumption: Calculate based on power and time of usage.
  • Example 1: Headlight of a car (50W) used for 1.5 hours.
  • Example 2: 6V bicycle bulb drawing 0.6A for 5 minutes.

Summary

• Conversion of electric energy into other forms across various devices.
• The significance of power ratings and energy consumption.
• Understanding the efficiency and loss due to resistance.
• Practical examples and calculations to reinforce learning.