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Torque and power are both measures of force.
- Torque is the energy applied when rotating an object around an axis or pivot point.
- Whereas power is the capacity to do a particular work.
- Torque and power are what motors produce when you turn the key and press the accelerator.
- Basically, Torque and power are two different ways of calculating force.
- Torque and power may appear to be difficult concepts to grasp, but they are fascinating, and we use them in our everyday lives.
| Table of Content |
Key Terms: Torque, Power, Force, Angle, Axis of rotation, SI unit, Horsepower, 1 Watt, 1 Newton, Scalar quantity, Vector quantity, Distance
Introduction to Torque
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Torque, also known as moment or moment of force, is a force that causes an object to rotate around its axis.
- Torque is employed, for example, while turning a door knob.
- Torque is a two-dimensional vector quantity with both magnitude and direction.
- The symbol for torque is τ.
- The unit of torque is Newton per meter symbolized as N-m or N m.
The following is the torque formula:
τ = Fr sinθ
Where,
- F refers to the force applied
- r refers to the distance covered in the area between the pivot and the point where the force is evaluated
- θ refers to the angle between F and r
- If we apply force in positions 1 and 2, it will not rotate the bolt.
- But if we apply force on positions 3 and 4, the bolt will rotate.
- Hence, we conclude that for anybody to start rotating something other than force is required.
- That something is known as torque.
Factors Responsible for Choosing the Right Torque
Torque is calculated as the product of the amount of force applied to the crankpin by the piston and the distance of that force from the center axis, or throws, which varies by crankshaft.
- If the throw remains constant, the piston will produce greater force, resulting in higher displacement.
- If the force on the piston remains constant, we can increase torque.
- Thus, we can raise the torque by escalating the distance between the pin and the crankshaft center.
Work, Energy, and Power Class 11 Notes PDF
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| Related Concepts | ||
|---|---|---|
| Moment of Force | Torque or Couple | Difference Between Mass and Volume |
| Relation between Moment of Inertia and Torque | Types of Motors | Helmholtz Equation |
Introduction to Power
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The rate at which work is completed is determined by power.
- Watt (W) is the SI unit of power, named after James Watt, who discovered it.
- A watt is defined as one joule of work done per second.
The equation for power is:
P = ΔE/Δt
Where,
- P refers to the power,
- ΔE refers to the change in energy,
- Δt refers to the change in time
Difference between Torque and Power
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The differences between torque and power are stated in the below table:
| Torque | Power |
|---|---|
| It is the force causing an object to rotate in a particular direction. | The rate at which work is completed is known as power. |
| It is a Vector quantity. | It is a scalar quantity |
| Torque can be calculated or determined by using a torque sensor or a torque meter. | Power can be determined by using an energy meter and multimeter. |
| Formula to calculate Torque: τ = Fr sinθ | Formula to calculate Power : P = ΔE/Δt |
| The SI unit of torque is Newton-meter (N-m). | The SI unit of power is Watt (W). |
Difference between Torque and Power in terms of Cars
Consider a car that travels at a constant speed.
- If it moves swiftly, it means a lot of force is being used to propel it ahead, meaning that the wheels are running very fast.
- The more rotations the wheels make as they spin, the faster the car accelerates.
- As a result, horsepower is measured by multiplying torque by the rate of work done, or rpm (revolutions per minute).
- When the wheel spins fast enough, the force pushing on the piston is uniform.
- When you spin the shaft faster while applying the same force at the same distance, more power is produced.
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Things to Remember
- Torque and power are two different ways of calculating force.
- Torque is a measure of force, while power is a measure of labor, representing force over time.
- Torque relates to the ability to perform work, whereas power refers to the pace at which work is completed in a given length of time
- The formula for Torque is τ = Frsin (θ) and for power it is P = ΔE/Δt.
- In physics, the torque imparted on an object is determined by the force itself (its magnitude and direction) as well as the location where the force is applied.
- Torque can be both positive or negative.
- It depends on the rotation.
Sample Questions
Ques. Define Torque. (2 marks)
Ans. The rotating equivalent of linear force is torque. It is also known as the moment of force. It expresses the rate of change of angular momentum supplied to an isolated body.
Ques. Define Power. (2 marks)
Ans. The amount of energy transferred or converted per unit of time is referred to as power. The watt is the unit of power in the International System of Units, equivalent to one joule per second.
Ques. What is the relationship between torque and power? (2 marks)
Ans. The rotating equivalence of linear force is torque. Work done over a period of time is referred to as power. The relationship between torque and power is inversely proportional. The scalar product of torque and angular velocity can be used to calculate the power of a rotating object. For instance: if the speed of a car increases, torque decreases. Torque and power both are ways of calculating force.
Ques. State some examples of Torque. (4 marks)
Ans. Torque is the force causing an object to rotate in a particular direction. Here are some examples of Torque used in daily life:
- When you open or close a bottle lid by twisting it. The same goes for taps.
- When a pencil is gripped and turned inside a sharpener. Torque is what makes everything with a crank work.
- When you pull on the thread quickly while spinning a top.
- When you open or close a door
Ques. Why does torque increase as RPM increases? (2 marks)
Ans. Horsepower is computed by multiplying torque by revolutions per minute (rpm) and dividing by a constant. Since an engine’s maximum speed is limited, providing more torque allows for more horsepower to be produced at lower rpms. This is the reason why “low-end torque” is quite difficult to produce more power at low speeds. Hence, if Torque increases RPM also increases with it.
Ques. What is the primary source of torque? (2 marks)
Ans. In physics, the torque imparted on an object is determined by the force itself (its magnitude and direction) as well as the location where the force is applied. You progress from the strictly linear concept of force as something that acts in a straight path (as when pushing a refrigerator up a ramp) to torque, which is its angular equivalent.
Ques. Why is torque referred to as a moment of force? (2 marks)
Ans. The product of a (physical quantity) and a (physical quantity) is defined as the moment (perpendicular distance). Consider the Moment of Inertia. Torque is the outcome of changing the physical quantity in the definition of the moment to “Force” ( product of Force and a perpendicular distance). As a result, Torque is defined as the instant of force.
Ques. Is it possible to have a negative torque? (2 marks)
Ans. Torque can be positive or negative, depending on the situation. A positive torque works counterclockwise, whereas a negative torque works clockwise. If you swapped these, it wouldn’t make much of a difference. Furthermore, the location on which the torque is calculated has an impact on it.
Ques. What are the main differences between torque and power? (2 marks)
Ans. Torque relates to the ability to perform work, whereas power refers to the pace at which work is completed in a given length of time. Torque is mostly used to accelerate a vehicle during its earliest phases of movement, whereas horsepower determines the rate of acceleration. The formula for Torque is τ – Frsin (θ), whereas for power it is P = ΔE/Δt.
Ques. Is higher torque associated with faster acceleration? (2 marks)
Ans. Torque is an important aspect of generating power from a car's engine since it represents the amount of load an engine can handle in order to generate enough power to rotate the engine on its axis. As a result, the more torque your car possesses, the faster it will accelerate. In other words, A vehicle with greater horsepower than torque will always be faster, as this provides acceleration and speed.
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