This article describes the important differences between power and torque. Two significant parameters that play a major role in the operation of engines and motors are power and torque. Power and Torque are interrelated terms. The torque is required to move heavy objects like large vehicles, and the Power is produced as a result of Torque which is used to increase the speed of the moving object.
What is Power?
Technically, Power is defined as the amount of work produced in a specific period of time. In simple words, power is the quantity of energy consumed by an object in a unit of time. Power is denoted by P. Its SI unit is watt or Joules/second (J/s). Therefore, the power generated by an electronic circuit or motor is given below.
Depending on the type of work done, Power is broadly classified into two categories as follows:
- Electric Power
- Mechanical Power
Electric Power
It is the type of work done or energy consumed by an electronic circuit. Electric power is further classified into – real power, reactive power, and apparent power.
- Real power (P) with a unit of Watt (W) is defined as the quantity of power actually released by the resistive load in an electric circuit.
- Reactive Power (Q) with the unit of volt-amperes reactive (VAR), is the amount of waste power in the form of heat loss produced by capacitors and inductors.
- Apparent power (S) is the sum of real power and reactive power and is represented by S, with the unit being Volt-Amperes (VA).
Figure 1 below shows the three types of electric power triangles.
Mechanical Power
It is defined as the rate at which work is done by an engine or motor after consuming energy generated by the fuel provided. The unit of measurement of mechanical power is Joules/second (J/s).
What is Torque?
Technically, Torque is a quantity that is defined as the rotational or circular force that is applied in order to rotate a shaft of the motor or engine. In simple words, Torque is the amount of force applied to an object to overcome the object’s rotational resistance and bring the stationary object to the motion.
For instance, heavy vehicles require more torque to start the movement of the vehicle, as compared to light-weight vehicles. Torque is also sometimes referred to as rotational force. The symbol of Torque is τ and its SI unit is Newton-meter (N-m). Figure 2 below illustrates the rotational effect of Torque applied. Hence, the Torque applied on an object is given by the following expression:
Torque can be also expressed as;
Based on angular acceleration, Torque can be of the following two types:
- Static Torque – When torque produces no angular acceleration on applying force to the object, it is referred to as a Static Torque. For example, Force is applied for the movement of the door hinges when it opened.
- Dynamic Torque – When torque produces angular acceleration when force is applied to the object, it is referred to as a Dynamic Torque. For instance, the acceleration of a car on a highway.
Difference between Power and Torque
The major differences between Power and Torque is described in the table below.
| Key | Power | Torque |
| Definition | Power is defined as the rate of doing work in a system (mechanical system/electric circuit). | Torque is defined as the turning force applied to spin a body-like shaft of a motor about its own axis. |
| Types | Electric power (reactive, apparent, and real powers) and Mechanical power. | Static Torque and Dynamic Torque. |
| Symbol | Power is represented by the symbol P. | Torque is represented by the symbol τ. |
| Unit | The SI unit of measurement of Power is Watt (W). The other unit of Power is Joules/second (J/s). | The unit of measurement of Torque is Newton-meter (N-m). |
| Formula | Power is given by the following formula, Power(P)=Work Done/Unit Time | Torque is given by the following formula, Torque(τ)=Force(F) X Distance(d) |
| Measuring Tool | Multimeters and wattmeters are used to measure the amount of power produced in watts or kilowatts. | A torque meter is used to measure the amount of torque generated. |
| Type of Quantity | Power is a scalar quantity, thus it has only magnitude and no direction. | Torque is a vector quantity, thus it has both magnitude and direction in which the object rotates. |
| Applications | Home appliances such as air conditioners, television, iron box, lamp, heater, etc., also in industrial power plants, and electric power grids. | Movement of vehicle wheels, motors, generators, steering wheels, and the opening of a door or cap of a bottle. |
Conclusion
Hence, this is all about Power and Torque. From the above discussion, we may conclude that there are several notable differences between Power and Torque, but the most significant difference is that Torque is the rotational force required to move bulky objects, while Power is the rate or speed at which work is done to keep the object in motion. Therefore, power and Torque have a direct and proportional relationship with each other.