Power vs Torque: Difference and Comparison

Power refers to the rate at which work is done or the rate at which energy is transferred. Power is measured in units of horsepower (hp) or kilowatts (kW). Torque refers to the twisting force that an engine can generate. Torque is measured in pound-feet (lb-ft) units or Newton meters (Nm).

Key Takeaways

  1. Power is the rate at which work is done, or energy is transferred, while torque is a rotational force that causes an object to rotate around an axis.
  2. Power depends on torque and engine speed, with higher torque and speed resulting in greater power output.
  3. Torque is more critical for acceleration and towing capacity, while power is important for top speed and maintaining high speeds.
Power vs Torque

What is Power?

Power refers to the ability or speed at which a machine can do its required work. Power can also be alternatively called horsepower. A vehicle’s power is directly proportionate to its speed and acceleration. 

In other words, when a vehicle is said to have high power, it also means that it will have top-notch speed and acceleration. One power or horsepower (hp) measures approximately 0.746 kilograms. Horsepower, or power, however, can be of two types:

  1. Mechanical horsepower
  2. Metric horsepower

The term Horsepower or Power was first used during the 18th century to draft a comparison between steam engines and draft horses. The term was curated by a Scottish engineer whose name was James Watt. Most countries now around the world use watts as a measure to define power. 

In modern days, power when opting to buy a car is so important because it will define how one’s car performs on the road. A car with fewer horsepower will have lesser speed and acceleration than one with more. Thus, if one travels a lot by land, then having a car with good horsepower is important to cover long distances.

power

What is Torque?

Torque can be defined as the force that is made by a car’s engine. It is the pulling force of the engine or a machine. The heavier the machine or vehicle is, the greater is the need for torque in its engines. Torques help with the spinning of initial inertia for acceleration. High torque energy is needed when a machine is performing with heavy workloads, or a car is working towards high inclined areas. Higher Torque helps heavy vehicles or machines easily get their job done.

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The term torque is derived from the Latin dictionary, which means ‘to twist.’ Thus signifying its job is done at initial acceleration. The word torque was first used in 1884 by the brother of lord Kelvin, James Thomson.

Torque is a rotating force of an object about its axis or at a fixed point. The unit of torque at which it is measured is Newton-meter, which also can be used as nm.

There are two types of torque. They are:

  1. Static Torque
  2. Dynamic Torque

Any torque that does not provide bifurcated acceleration is static torque. At the same time, the torque that provides angular acceleration is dynamic torque.

Difference Between Power and Torque

  1. Power is the ability or speed at which a machine can do its required work, while torque is the rotating force of an object about its axis or at a fixed point.
  2. The International System of Units for power is the watt, while the International System of Units for torque is the Newton meter.
  3. The symbol that represents power is the exponent symbol (^), while the symbol that represents torque is the Greek letter tau (τ).
  4. Power is a greater concept as it defines the whole process of ability or speed of a machine, while torque is a narrower concept as it defines a fixed point at an axis during initial acceleration. 
  5. The mathematical formula for power is work divided by elapsed time, while the mathematical formula for torque is radius multiplied by force multiplied by sin theta. (Sin θ).

Comparison Between Power and Torque

Parameter of ComparisonPowerTorque
DefinitionPower is the ability or speed at which a machine can do its required work. Torque is defined as the rotating force of an object about its axis or at a fixed point.
SymbolThe symbol of power is ^.The symbol of torque is τ.
SI unitThe SI unit of power is Watt.The SI unit of torque is Newton-meter.
ConceptPower is a wider concept as it covers a machine’s whole ability or speed.Torque is a narrower concept as it only focuses on a fixed point during initial acceleration.
FormulaThe formula of power is P = E/t Where, P= Power E= Energy t= time in seconds.The formula of torque is Γ=r×FxSinθ.
First usedThe term power was first used by James Watt, a Scottish engineer.The term torque was first used by James Thomson, brother of lord Kelvin.
DiscoveredThe term power was first discovered in the 18th century.The term torque was first discovered in 1884.
References
  1. https://www.sciencedirect.com/science/article/pii/S136403211500458X
  2. https://ieeexplore.ieee.org/abstract/document/1469805/
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Last Updated : 29 July, 2023

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