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General SciencePhysics
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Which of the following is a unit of power?

A

Joule

B

Watt-second

C

Newton

D

Watt

Correct Answer

ЁЯФм SC тАв Science Concept & PrincipleGeneral SciencePhysics
Option D

Watt

Quick Summary:

Power is defined as the rate at which work is performed or energy is transferred ┬╖ Its SI unit is the Watt (W), named after James Watt, which is equivalent to one joule per second.

ЁЯФмSCScience SolutionConcept & Principle
ЁЯТб Explanation

Power is defined as the rate at which work is performed or energy is transferred ┬╖ Its SI unit is the Watt (W), named after James Watt, which is equivalent to one joule per second.

ЁЯТб Everyday Analogy (Real-World Intuition)

If work is the total amount of bricks carried to the top of a building, power is how fast you carry them; a crane has higher power than a person because it moves more bricks in the same amount of time.

ЁЯза Memory Mnemonic / Shortcut Aid

WET: Work = Energy, Time involved in Power.

ЁЯФв Key Formulas

P=WtP = \frac{W}{t}P=tWтАЛ тАФ Power equals Work divided by time

P=I2RP = I^2 RP=I2R тАФ Electrical power dissipation in a resistor

P=FтЛЕvP = F \cdot vP=FтЛЕv тАФ Instantaneous mechanical power

тЪЩя╕П Working Principle

Power measures the time derivative of energy consumption ┬╖ When a system performs 111 Joule of work in 111 second, the power dissipated is 111 Watt ┬╖ Mathematically, it relates force, displacement, and time through the relationship P=Wt=FтГЧтЛЕvтГЧP = \frac{W}{t} = \vec{F} \cdot \vec{v}P=tWтАЛ=FтЛЕv, where FтГЧ\vec{F}F is force and vтГЧ\vec{v}v is velocity.

ЁЯУМ Key Points
  • тЦ╕

    Power is a scalar quantity.

  • тЦ╕

    The SI unit of power is Watt (W) = JтЛЕsтИТ1J \cdot s^{-1}JтЛЕsтИТ1.

  • тЦ╕

    Horsepower (hp) is a common non-SI unit where 1┬аhpтЙИ746┬аW1 \text{ hp} \approx 746 \text{ W}1┬аhpтЙИ746┬аW.

тЬЕ Advantages
  • тЦ╕

    Provides a standard measure for engine and appliance performance.

тЭМ Disadvantages / Limitations
  • тЦ╕

    Does not indicate the total energy capacity of a system, only the rate of usage.

ЁЯЫая╕П Applications / Uses
  • тЦ╕

    Rating electrical appliances like light bulbs and heaters.

  • тЦ╕

    Measuring the output of mechanical engines and motors.

ЁЯУД Additional Information
  • тЦ╕

    Joule (Option A) is the unit of Energy.

  • тЦ╕

    Watt-second (Option B) is another unit of Energy (1┬аWs=1┬аJoule1 \text{ Ws} = 1 \text{ Joule}1┬аWs=1┬аJoule).

  • тЦ╕

    Newton (Option C) is the SI unit of Force.

ЁЯУК Diagram / Illustration
Understanding Power and its SI Unit 1 Definition of Power Power is the rate of doing work or transferring energy: P = W / t 2 SI Unit Derivation 1 Watt (W) = 1 Joule / 1 Second (J/s) 3 Key Relationships P = F ├Ч v (Mechanical) | P = I┬▓R (Electrical) 4 Conclusion The SI unit of Power is Watt (W) Correct Answer: D) Watt
тЬЕ

D is correct тАФ Watt is the standard SI derived unit for measuring power.

Core Concepts Used
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Power Work-Energy Theorem SI Units
ЁЯТб EXAM TIP

Always distinguish between energy units (Joule, kWh, Calorie) and power units (Watt, Horsepower) to avoid common trap questions in Physics.

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