Difference WikiPhysics

Difference Between Work and Power

Main Difference

The main difference between Work and Power is that Work is the total amount of energy required to move an object from one place by exerting external force, and its SI unit is Joule, whereas Power is the rate of doing work and its SI unit is Watt.

Work vs. Power

Work is the total amount of energy that is used to shift an object from one place to another by applying an outside force, for example: if a carton of books is moved from the lounge into the study room. However, power is the rate at which work is done; for example, if the book carton is moved slowly, it means a less amount of power is applied and will require more time. But if the container is moved fastly, it means more power is needed to do the work quickly.

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The System International (SI) unit of work is Joule (J). The symbol of work is denoted by W whereas, the System International (SI) unit of Power is Watt (W), and the symbol of power is denoted by P. The other bigger units of work include one kilojoule = 1000 J = 10 J, 1 mega Joule = 1000 000 J = 10 J and, electron volt (eV). While other bigger units of power counts on 1 Kilowatt = 1000 W = 10³ W, 1 Megawatt = 1000 000 W = 106 W, 1 horsepower = 746 W, and GW.

Work is the outcome of force (F) and displacement (S) in the direction of force thus the equation can be written as (Work done = Force x displacement), or (W = FS) whereas, power is the fraction of work and time (work/time), so the equation is written as (Power = Work done / Time taken) or (P = W / t).

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Comparison Chart

WorkPower
Work is known as the total amount of energy used to move an object from one place to another with external force.Power is known as the amount of degree at which work is done.
Symbol
The symbol of work is W.Power is denoted by P.
SI Unit
The SI Unit of work is Joules (J).The SI unit of power is Watt (W).
Equation
Work = force × Displacement.Power = Work/Time
Other Units
Electron volt (eV), kWh, MWh, GWhkW, MW, GW, horsepower (hp)
Relationship with Energy
W=ΔKEP = E/t
SI Base Unit
Kgm²s -²Kgm²s -³

What is Work?

In the field of physics, work is the force required for the displacement of a body, and it is a scalar quantity with equation W = F*S. If the force applied is constant, the work done will be equal to the scalar product of the external force applied to the body and the displacement that occurs due to that force. The examples from daily life can be the gardener running grass cutter machine through the garden, and an ox pulling a plow in the fields.

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Some actions are not considered as work; therefore, to do work, a force is always required on a body, causing its movement. A man is pushing against the wall to do isometric exercise, but the wall cannot be moved, so it doesn’t count as work. According to physics, a ball thrown from the roof of the house hits the ground is considered as work. In this phenomenon, gravity, as a force, is acting on the ball, enables the ball to move in a downward direction.

Joule (J) is the unit of work), it can be stated as the amount required for work is one joule (1J) when a one newton (1N) force is applied to the object to move the object one meter (1m) towards the direction of force, e.g., 1 J = 1 N x 1 m. But it creates confusion with the unit of torque, which is also N.m, making it difficult to decide whether the unit is a torque measurement or a measurement of work.

What is Power?

In the field of physics, it is the rate at which work is done or the work that is done according to per unit time. According to the System International (SI), the unit of power is Watt (W) that equals Joule per second (1 Js -¹).

Its equation can be written as (Power = Work done / Time taken) or (P = W / t). The SI unit of power is Watt (W), which can be described as the amount of power required is one watt (1W) to do work at the rate of 1 joule per second (1 Js -¹).

In order to extract the working capacity of appliances such as, electric oven, or a generator, a light bulb, a water heater, or a fan, the understanding of power is essential. Energy cannot indicate the working capacity of such appliances because the utilization of energy always relies on time.

As the appliances are constructed in a manner that they work at fixed power, the energy utilization changes (increases) along time, but the power persist continually. Therefore, energy utilization can be simply measured when power is known. Moreover, the power capacity of power stations is denoted in bigger units, e.g., Megawatt.

Power can be of many types, such as electrical, mechanical, and that of a rotating body; Electrical power can be expressed as p=I²R=VI=V²/R, where P=power, I=current, V=voltage. Mechanical power can be expressed as P=F.V where F = force on the object, V = velocity of the object.

Key Differences

  1. Work is the amount of force required to move an object by applying outside force, while power is the degree at which work is done.
  2. Joule (J) is the SI unit of work, whereas Watt (W) is the SI unit of power.
  3. The work is denoted by the formula W = F.S; conversely, power is indicated by formula P = W/t.
  4. The other units of work are kWh, MWh, GWh, Electron volt (eV), while other units of power are kW, MW, GW, horsepower (hp).
  5. The symbol of work is (W); on the flip side, the symbol of power is (P).
  6. The relationship between work and energy can be defined as work done on a body is equal to the variation in kinetic energy (KE). Whereas, the relationship between power and energy can be explained as the multiplication of power with time can give energy; similarly, the division of energy by time provides power.
  7. The relationship between work and energy is expressed as W=ΔKE or, W=Ki−Kf where W = work done, Ki= initial Kinetic Energy, Kf = Final Kinetic Energy, and ΔK = difference in Kinetic Energy; on the other hand, the relationship between power and energy is expressed as P = E/t.
  8. The SI Base unit of work is denoted as Kgm²s -² conversely, Kgm²s -³ is the base unit of power.

Conclusion

The above discussion concludes that both work and power are the terms of physics, but they differ in characteristics as work is the force applied to move n object, and its SI unit is Joule, whereas power is the rate at which work is done, and its SI unit is Watt. The equation of work is expressed as Work = Force × Displacement but, the equation of power as Power = Work/Time.

Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss