What is the difference between RPM and Torque? Interview questions on RPM and Torque.

What is the difference between RPM and Torque?

What is RPM and Torque, and what is the difference between RPM Torque? I will try to understand it in very simple words.

RPM Torque difference in motor

RPM- Stands for rotations/revolutions per minute. This is a measurement of how fast your engine is rotating.

Torque- Torque is a measurement of rotational force. Torque is applied to your wheels which makes them rotate. The more torque a car has the faster it accelerates, the more horse power a car has, the higher its top speed will be.

Relationship between RPM and Torque:

Torque = (Horsepower × 5252) ÷ RPM

Whenever we talk about a motor or we talk about an engine, then at that time we get to hear both the words Torque and RPM in a lot of places. Now, what are these two, and what is the difference between these two? We will know this one by one.

What is RPM?

If we talk about RPM first, what is RPM? So almost all the people are fully aware of it, but still, we remain a little confused. So today you will be able to remove that confusion too.

First of all, if we know the full name of RPM, then it is Rotation Per Minute and in many places, it is also called Revolutions Per Minute.

However, if I tell you a little better about RPM. So if we are ever talking about the motor or we are talking about our bike, then in both cases, the meaning of RPM is different.

First of all, we know about the motor, what is the RPM in the case of the motor?

What is the meaning of RPM in Motor?

For example, suppose we have a motor now and we know that there is a rotor in the middle of this motor. And when we give electrical supply to this motor, due to that the rotor of our motor starts rotating in a circular motion.

Now that our rotor is rotating means that it is doing rotation, how many times that rotation is happening in 1 minute, that is what we call RPM. Meaning, how many times the rotor of our motor is rotating in a minute, the number of revolutions of this motor is called RPM.

Also read- Differences between AC motor and DC motor, which you can easily tell even within the interview Questions.

If a motor can make only one revolution in 1 minute, then you would say the RPM of that motor is 1. And if a motor spins 2 times in 1 minute, then the RPM of that motor will be 2. But, our motor is not of such a low rpm, our motor is running at about 1000-2000 RPM which means every 1 minute the rotor of the motor rotates 1000-2000 times.

After this, if we know the RPM in the case of bike-car. This is also very important because some of us have the wrong information about it.

We think that whenever we talk about a car or a bike, then the tire of our bike or car at that time, the number of times that tire rotates in 1 minute is our RPM.

But, it is not like this, whenever we talk about a bike or car, who spins the tire in it? So the engine attached to its tire rotates. So how many times the engine inside the car is rotating in 1 minute, that is what we call the RPM of the vehicle.

You have to keep in mind one thing that many of our vehicles have an RPM meter installed inside, which tells at which RPM our vehicle is running.

RPM meter in Bike So you do not have to get confused at this place, because the RPM of the vehicle which is showing in our meter tells the speed of engine rotation means the RPM of the engine.

So I hope that now what is the RPM in the motor, it must have been completely cleared. Also, I want to tell you one thing, that in many places RPM is called rotation per minute, but in some places, it is called revolution per minute. So you don't have to get confused at this time, it is minute on revolution and minute on rotation, both of them mean completely the same. Both tell us how many times the object will rotate in 1 minute.

But now the next most confusing question in front of us is what is torque?

What is Torque?

Torque is very easy to understand, if you ever want to answer it in just one word, then you can say that torque is our twisting force. By the way, what is the meaning of this twisting force and torque, now we talk about it well.

For example, suppose a box is placed in front of you, and now a man comes and pushes it forward.

So when that person puts pressure on this box in the forward direction, because of this, that box moves forward. This means that box is moving forward in the straight direction and when our box will move in a straight direction then we call it linear motion.

Linear motion means that an object is moving in a straight line. And you should also know one thing that whenever this type of condition occurs i.e. there is a condition of linear motion, then we call the pressure exerted at this time a force.

But the same if we talk about what is torque after all?

So, now to understand what will happen in the case of torque, let us go back to the earlier example of a box. In that example, the box was going straight direction meaning linear motion, so we called the pressure exerted by that force.

But now if we apply pressure on an object, it starts rotating instead of linear motion, then we call it rotation motion.

And whenever such a condition is created in which we apply pressure on an object, and by applying our pressure, that object does not go in linear motion means straight direction, but rotation motion means stay rotating, then at that time we call the force (pressure) on the object as torque.

Now let us understand all these things with the example of a practical motor.

So as we all know that the motor which is there, that motor rotates in our circular motion which means that the motor does our rotation motion. So now in this case we will say that the motor we have produces torque.

You all must have noticed one more thing. Whenever we talk about the engine or any motor, we do not talk about force there. We do not do this because of our engine or our motor, both of them do the motion, they do it in the rotating direction. So for this reason we use the word Torque here.

So, now if someone asks you about RPM Torque, then you have to speak in simple words.

What is RPM Torque and Difference?

RPM and Torque are inversely proportional.

RPM vs Torque Graph

Torque- Torque is our twisting force. If we look at it with the example of a motor, then - by giving electrical supply to the motor, a magnetic field is generated in the motor, due to that magnetic field, pressure is applied to the rotor of the motor, and due to that pressure, our rotor experiences a twisting force. At this time, the twisting force that is rotating or applying pressure to our rotor is our torque.

RPM- If we talk about RPM, then the full name of RPM is Rotation Per Minute or Revolutions Per Minute. And when we talk about RPM in the motor, then at that time we tell the speed of rotation of the rotor of the motor. Meaning how many revolutions the rotor will complete in 1 minute, the same will be the RPM of that motor.

Also read- What is the use of Strips on AC Motor? Why only AC motor needs cooling?

Interview questions on RPM and Torque.

1) Which is better torque at low rpm or torque at high rpm?

Ans- At lower RPM equates to higher torque and thus lower horsepower while making higher RPM power outputs less torque and higher top horsepower.

2) How are torque and RPM related?

Ans- Horsepower equal to torque multiplied by rpm. H = T x rpm/5252, where H is horsepower, T is Torque in pound-feet, rpm is how fast the engine is rotating, and 5252 is a constant that makes the units jibe. To make more power an engine needs to generate more torque, operate at higher rpm, or both.

3) Why does torque drop at high rpm?

Ans- At high RPM, Volumetric Efficiency declines because the engine can't breathe any faster, and mechanical efficiency also declines at higher RPM, due to increased frictional resistance. This further reduces torque at the output.

4) What is the advantage of high torque?

Ans- Having high torque force as the engine rotation (RPM) increases makes transporting heavy loads far easier and more efficient. Easier for driving up steep inclines - Having extra torque is also what creates enough power to get a vehicle going, particularly when moving up steep inclines.

5) Is torque a speed?

Ans- Torque is the rotational equivalence of linear force. Speed measures the distance covered in unit time. The relation between torque and speed is inversely proportional to each other. The torque of a rotating object can be mathematically written as the ratio of power and angular velocity.

6)Can you have negative torque?

Ans- Torque can be positive or negative. Let us say that a positive torque would make a stationary object rotate counter-clockwise and a negative torque would make it rotate clockwise.

7) What determines the torque of an electric motor?

Ans- Electric motors operate on magnetism, electrostatics, and piezoelectricity. In magnetic motors, magnetic fields are formed in both the rotor and the stator. The product between these two fields gives rise to a force, and thus a torque on the motor shaft.

8) Do electric motors have more torque?

Ans- Electric vehicles generate much more torque than gas vehicles, which is important because torque is what drives the vehicle forward.

9) How can we increase the torque in an electric motor?

Ans- The way to increase the torque that the motor delivers, mechanically, would be:

To increase the diameter of the wire in the windings (which is to say, completely remanufacture the motor)
To have the output shaft coupled to a gear reduction setup, which would lower the final drive RPMs, but increase the torque.