Overview
This lecture explains the concept of power in physics and demonstrates how to calculate power using energy transferred or work done, with practical examples and formulas.
What is Power?
- Power is the rate at which energy is transferred or work is done.
- The unit for power is the watt (W), where 1 watt equals 1 joule per second.
Power Formulas
- Power (W) = Energy transferred (J) / Time (s)
- Power (W) = Work done (J) / Time (s)
- These formulas must be memorized for exams; they are not provided.
Calculating Power: Examples
- Example 1: A Bunsen burner transfers 250,000 J in 500 s; power = 250,000 / 500 = 500 W.
- Example 2: Another Bunsen burner transfers 180,000 J in 500 s; power = 180,000 / 500 = 360 W.
- Example 3: Car brakes do 40,000 J work in 5 s; power = 40,000 / 5 = 8,000 W.
- Example 4: Motor A lifts 500 J in 40 s; power = 500 / 40 = 12.5 W. Motor B lifts 500 J in 60 s; power = 500 / 60 = 8.3 W.
Key Terms & Definitions
- Power — The rate of energy transfer or work done, measured in watts (W).
- Watt (W) — The unit of power, equal to one joule per second.
- Joule (J) — The unit of energy or work.
- Work Done — The amount of energy transferred by a force moving an object.
Action Items / Next Steps
- Memorize the power formulas for exams.
- Practice more power calculation questions from the recommended workbook.