CIE iGCSE Co-ordinated Sciences-P1.6.4 Power- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-P1.6.4 Power – Study Notes
CIE iGCSE Co-ordinated Sciences-P1.6.4 Power – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- Define power as work done per unit time and also as energy transferred per unit time; recall and use the equations
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Definition of Power
Power is the rate at which work is done or the rate at which energy is transferred.
- The unit of power is the watt (W), where \( 1~\text{W} = 1~\text{J/s} \).
Equations for Power:
\( P = \dfrac{W}{t} \) or \( P = \dfrac{E}{t} \)
- \( P \) = power (watts, W)
- \( W \) = work done (joules, J)
- \( E \) = energy transferred (joules, J)
- \( t \) = time taken (seconds, s)
Alternative Formula (Force and Velocity):
- When a force moves an object at a constant velocity,
- \( P = F \times v \)
- \( F \) = force applied (newtons, N)
- \( v \) = velocity of the object (m/s)
Example:
A motor does \( 600~\text{J} \) of work in \( 20~\text{s} \). Find the power of the motor.
▶️ Answer/Explanation
Using \( P = \dfrac{W}{t} \):
\( P = \dfrac{600}{20} = 30~\text{W} \).
The motor’s power output is \( 30~\text{W} \).
Example:
An electric kettle transfers \( 9000~\text{J} \) of energy to boil water in \( 3~\text{minutes} \). Calculate its power rating.
▶️ Answer/Explanation
Step 1: Convert time
\( 3~\text{minutes} = 3 \times 60 = 180~\text{s} \).
Step 2: Apply formula
\( P = \dfrac{E}{t} = \dfrac{9000}{180} = 50~\text{W} \).
The kettle’s power is \( 50~\text{W} \).
Example:
A car engine exerts a driving force of \( 2000~\text{N} \) to keep the car moving at a constant speed of \( 15~\text{m/s} \). Find the power output of the engine.
▶️ Answer/Explanation
Using \( P = F \times v \):
\( P = 2000 \times 15 = 30000~\text{W} \).
The engine delivers \( 30~\text{kW} \) of power.