Power MCQs Quiz | Class 9
Class IX Science (Code 086) Unit III: Motion, Force and Work. This quiz covers the topic of Power, including its meaning, the unit watt, and various examples. Test your understanding, check your score, and download the answer key PDF for revision.
Overview of Power
In physics, Power is defined as the rate of doing work or the rate of transfer of energy. It measures how fast work is done. If two machines do the same amount of work, the one that does it in less time has more power.
Formula: Power = Work done / Time taken (P = W/t)
The Unit of Power: Watt
The SI unit of power is the Watt (symbol: W). It is named after James Watt.
- Definition of 1 Watt: Power is said to be 1 Watt when 1 Joule of work is done in 1 second.
- 1 W = 1 J/s
- Higher Units:
- 1 kilowatt (kW) = 1000 Watts
- 1 megawatt (MW) = 1,000,000 Watts
Commercial and Other Units
| Unit Name | Symbol | Value in Watts |
|---|---|---|
| Watt | W | 1 W |
| Kilowatt | kW | 1000 W |
| Horsepower | hp | 746 W |
Horsepower is an older unit often used to describe the power of engines and motors.
Quick Revision Points
- Power is a scalar quantity; it has magnitude but no direction.
- The power of an agent measures how fast it can convert energy.
- Average Power = Total work done / Total time taken.
Extra Practice Questions
- Define 1 Watt of power.
- A lamp consumes 1000 J of electrical energy in 10 seconds. What is its power?
- What is the power of an engine that does 6000 J of work in 2 minutes?
- Convert 2 horsepower into watts.
- Differentiate between work and power.
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