IB MYP Integrated Science- Physics- Power and efficiency-Study Notes - New Syllabus
IB MYP Integrated Science- Physics – Power and efficiency -Study Notes – New syllabus
IB MYP Integrated Science- Physics – Power and efficiency -Study Notes -As per latest Syllabus.
Key Concepts:
Power and Efficiency
IB MYP Integrated Science -Concise Summary Notes- All Topics
Power
Power is the rate at which work is done or energy is transferred.
Formula
\( P = \dfrac{E}{t} \)
- \( P \) = power (watts, W)
- \( E \) = energy (joules, J)
- \( t \) = time (seconds, s)
Electrical Power
\( P = VI \)
- \( V \) = voltage (V)
- \( I \) = current (A)
Key Concepts
- Higher power → faster energy transfer
- 1 watt = 1 joule per second
- Used to describe performance of machines and appliances
Example:
A device uses 200 J of energy in 10 s. Find power.
▶️ Answer/Explanation
\( P = \dfrac{200}{10} = 20 \, \text{W} \)
Final Answer: \( \boxed{20 \, \text{W}} \)
Example:
A circuit has voltage 10 V and current 2 A. Find electrical power.
▶️ Answer/Explanation
\( P = 10 \times 2 = 20 \, \text{W} \)
Final Answer: \( \boxed{20 \, \text{W}} \)
Efficiency
Efficiency is the ratio of useful output energy (or power) to total input energy (or power), usually expressed as a percentage.
Formula
\( \text{Efficiency} = \dfrac{\text{Useful Output}}{\text{Total Input}} \)
\( \text{Efficiency (\%)} = \dfrac{\text{Useful Output}}{\text{Total Input}} \times 100 \)
Key Concepts
- Efficiency is always less than or equal to 100%
- Some energy is always lost (usually as heat)
- Higher efficiency → less energy wasted
Example:
A machine takes 500 J of energy and produces 400 J useful output. Find efficiency.
▶️ Answer/Explanation
\( \text{Efficiency} = \dfrac{400}{500} \times 100 = 80\% \)
Final Answer: \( \boxed{80\%} \)
Example:
A motor has 60% efficiency. If input energy is 1000 J, find useful output.
▶️ Answer/Explanation
\( \text{Output} = \dfrac{60}{100} \times 1000 = 600 \, \text{J} \)
Final Answer: \( \boxed{600 \, \text{J}} \)