13 Facts on Torque Direction: Magnetic, Electric & How to find


In the present article, we are going to discuss about the facts on direction of torque in the magnetic and electric fields.

We know that it is possible to rotate an object about its axis, the force responsible for this is usually termed as torque. The torque gives rise to angular acceleration. The torque basically corresponds to the rotational force that is responsible for the rotational motion about an axis known to be the axis of rotation.

The following section deals with the few general facts associated with direction of torque.

Direction of torque

As torque is a vector, it is believed to have a particular direction. Mathematically, we can explain torque as a vector that is resulted when we take the cross product of the radial distance vector with the force vector. The vector that we get, which is nothing but torque, is basically orthogonal to the vectors involved in the cross product. The vector can be seen pointing towards the page or outside the page.

The next part explains the two direction of torque.

What are the two direction of torque?

As we already know, torque represents a vector quantity. The evaluation of torque value is a combination of evaluation of both directions as well as magnitude. In general, the direction determined seems to be perpendicular with respect to the applied force and radius from the axis.

The following part deals with the direction of torque with respect to the force.

Direction of torque concerning force

The calculation of torque involves the determination of both directions as well as magnitude. In general, the direction determined seems to be perpendicular with respect to the applied force and radius from the axis. The angular velocity and change in the angular velocity produced due to the action of torque are also in the same direction as the direction of torque.

The next section tells why the direction of torque is always perpendicular to force.

Is torque always perpendicular to force

The direction of torque determined seems to be perpendicular with respect to the applied force. The direction of torque is conveniently assigned by using the right-hand rule, which states that the fingers in the right-hand curl along the direction that points to the radius as well as the applied force, and then the direction of torque is represented by the thumb of the right hand.

Let us now discuss another fact regarding the direction of torque.

Why is the direction of torque perpendicular to force?

The torque is conveniently assigned the direction using the right-hand rule. Mathematically, we can explain torque as a vector that is resulted when we take the cross product of the radial distance vector with the force vector. The vector that we get, which is nothing but torque, is basically orthogonal to the vectors involved in the cross product. The vector can be seen pointing towards the page or outside the page.

The following part deals with the evaluation of direction of torque.

How to find the direction of torque?

The direction in which the torque orients or in simple words, points is usually decided by the force in action The direction of torque is conveniently assigned by using the right-hand rule, which states that the fingers in the right hand curl along the direction that points to the radius as well as the applied force. The direction of torque in which it orients or in simple words, points is given by the thumb.

The length of the lever arm is ‘r’ and ‘θ’ is that angle which is made by the force vector with the level arm then,

                                                                                                                    τ = F.r.sinθ

Problem: If the force is applied, F= 5N and the length of the lever arm is r=4m. Find the torque when the angle between the force vector and radius vector is 30°.

Solution: We know that, τ = F.r.sinθ

Now, substituting the given values in the above equation, we get,

                                           τ = 5 x 4 x sin 30°

                                        τ = 10 N-m

The following section describes the method to find the direction of torque associated with a dipole in an arbitrary magnetic field.

The direction of torque in the magnetic field

Torque is a vector that is resulted when we take the cross product of the radial distance vector with the force vector. When a current loop or a magnetic dipole is assumed to be present in an arbitrary magnetic field, the loop develops a tendency by the impact of which it orients according to the field direction in the proximity of that field.

Then the direction of torque associated can be determined with the help of a very familiar right-hand rule.

 

How to find the direction of torque in the magnetic field?

In order to calculate the direction of torque in a dipole placed in a magnetic field, the following theory is followed, The direction of torque associated can be determined with the help of a very familiar right-hand rule. Here, we are supposed to fold our fingers in the direction of the current loop after the orientation that is placed in the magnetic field. The formula used is,     τ = m × B = |m||B| sinθ.

Where m- magnetic moment and B- magnetic field are applied.

When a current loop is said to be placed in a magnetic field, it is believed that the loop tends to orient according to the field direction due to the influence of that field.

Problem:

If the magnetic field intensity in which a magnetic dipole is kept making an angle of 30° is 3 × 10-4 T. Find the direction of torque acting on the dipole when the dipole moment is given to be 0.335 × 10-3 A-m?

Ans:  Electric field, B = 3 × 104 T

           Angle between dipole and magnetic field, θ = 30°

          Magnetic moment= 0.335 × 10-3C-m

    τ = |m||B| sinθ.

      = (0.335× 10-3  A-m)(3 × 104 T) sin(30°)

      =5 Nm

The direction of torque in the uniform electric field

The theory for determining the direction of torque in a homogeneous electric field is given below, A dipole, when placed in a uniform electric field, is said to acquire a translational equilibrium due to the implication of equal magnitude of electric pressure in both the directions on positive and negative charges. Thus, the net pressure is believed to be zero, but it is said to spin with an angular velocity.

Both the force and radius are responsible for the magnitude and direction of torque.

How to find the direction of torque in an electric field?

In order to calculate the direction of torque in a dipole placed in an electric field, we follow the below-mentioned method, The perpendicular distance may be referred to as the level arm. When we take the product of the level arm with the force applied, we get the torque. Here, the torque is given by τ= P.E.sinθ. ‘P’ is the dipole moment, and ‘E’ is the applied electric field.

Problem:

If the electric field intensity in which an electric dipole is kept making an angle of 30° is 3 × 104 N ⁄ C. Find the torque acting on the dipole when the dipole moment is given to be 0.335 × 10-3C-m?

Ans:  Electric field, E = 3 × 104 N ⁄ C

           Angle between dipole and electric field, θ = 30°

          Dipole moment= 0.335 × 10-3C-m

    τ = P.E.sinθ

      = (0.335× 10-3C-m)(3 × 104 N ⁄ C) sin(30°)

      =5 Nm

Next, we shall see the direction of torque in the electric dipole.

The direction of torque in the electric dipole

Torque is a vector that is resulted when we take the cross product of the radial distance vector with the force vector. A dipole, when placed in a uniform electric field, is said to acquire a translational equilibrium due to the implication of equal magnitude of electric pressure in both the directions on positive and negative charges. Here, the torque is given by τ= P.E.sinθ. P is the dipole moment, and E is the applied electric field.

Both the force and radius are responsible for the magnitude and direction of torque.

The direction of torque on a current loop

In order to calculate the torque in a current loop placed in a magnetic field, the following theory is followed, The torque associated can be determined with the help of a very familiar right-hand rule. Here, we are supposed to fold our fingers in the direction of the current loop after the orientation that is placed in the magnetic field. It shows that the torque is acting in the left direction, following the direction that our thumb points.

When a current loop is said to be placed in a magnetic field, it is believed that the loop tends to orient according to the field direction due to the influence of that field.

How to change the direction of torque wrench?

A fastener such as a nut or a bolt is implicated by a particular quantity of torque with the help of a tool known as the torque wrench. A wrench is usually provided with a handle, and by twisting and rotating the handle, we could be able to adjust the wrench, followed by changing the direction of the torque wrench. This is possible as we achieve the compression of the spring through the handle so that it requires more torque in order to release the ball.

Over time we can observe a weaker pressure on the spring if the wrench is stored due to loading.

The next part deals with the frequently asked questions regarding the direction of torque.

Mention the types of torque.

There are basically two different kinds of torque that are given below,

Static torque: A torque that cannot give rise to an angular acceleration is generally considered static torque. For example: when we need to push a door that is closed, the torque that we apply to do so is a static torque.

Dynamic torque: In contrast, a torque that is capable of generating an angular acceleration is considered to be the dynamic torque. Example: In a racing car, the drive shaft that is present generally tends to exhibit dynamic torque.

How can you explain torque in detail?

In order to explain the torque in detail, let us consider the example of two forces applied in opposite direction on an object. Here, When the magnitude of both the forces F1 and F2 are equal, then the net force on the object is seen to be zero, and it will be in equilibrium ( translational). Even though it is said to be in translational equilibrium, it is acted by force, generally termed as the moment of force or torque, which makes it to rotate.

How can you explain torque by taking an example?

Let us consider an example of a door and try to understand the concept of torque. In order to rotate the door, we may need a larger force when we apply force at a point that is closer to the hinge. The direction in which the force is applied also influences the amount of force required

We may need a smaller force when the axis joins the point where force is applied, and the hinge is perpendicular to the direction of torque.

 How has the torque been calculated?

Torque value depends on the magnitude of applied force as well as the perpendicular distance from the point at which you apply the force. The perpendicular distance may be referred to as the level arm. When we take the product of the level arm with the force applied, we get the torque. The length of the level arm is ‘r’ and ‘θ’ is that angle which is made by the force vector with the level arm then,

                                                                                                                    τ= F.r.sinθ

How do you explain the concept of torque in a car?

In general, an expression for a rotational or a twisting force can be regarded as a torque. Torque is said to be created in a vehicle when engines constituting those vehicles tend to rotate about an axis. It is basically considered to be the strength of the vehicle. Huge trucks with heavy loads are powered to undergo a motion through torque.

What are the applications of torque?

Some of the applications of torque may be as follows,

  • Gyroscopes
  • While riding a bicycle
  • A swinging pendulum
  • A flag flying when attached from one side
  • A parachute
  • In seesaws

Differentiate between the torque and the moment.

Torque is nothing but a special case of the moment. The torque, in general, is associated with the axis of rotation corresponding to the rotation. In contrast, the moment is just related to being achieved by an external force that gives rise to rotation.

Is torque a form of energy?

Torque cannot be taken as energy as it is a vector that is resulted when we take the cross product of the radial distance vector with the force vector. Mathematically, we can explain torque as a vector that is resulted when we take the cross product of the radial distance vector with the force vector. The vector that we get, which is nothing but torque, is basically orthogonal to the vectors involved in the cross product. The vector can be seen pointing towards the page or outside the page.

How can you differentiate torque and force?

The force influences the value of torque, but both are not the same. In rotational mechanics, we can say that the counterpart of the force is nothing but the torque. The property of force that enables it to cause a rotation or a twist about an axis is simply the torque; this might be the basic difference between them.

Name some of the examples of torque in our everyday life.

A few examples depicting torque can be given below,

  • When we open a bottle cap
  • A steering wheel, when tried to turn
  • While riding a bicycle
  • A swinging pendulum
  • A flag flying when attached from one side
  • A parachute
  • In seesaws

How is torque related to force?

The property of force that enables it to cause a rotation or a twist about an axis is simply the torque. The expenditure of force that takes place in order to spin an object about an axis is nothing but torque. An object accelerates by the influence of force, which is the case in linear kinematics, Whereas, whereas, in angular kinematics, the same action is performed by the torque.

Mention some of the characteristics of a torque

The characteristics that are associated with the torque are,

  • Torque is basically a vector quantity
  • The force acting along the axis of rotation determines the orientation of the torque vector.

What do you mean by positive and negative torque?

Torque can be positive and negative depending upon the direction of the force. We get a positive torque when the force responsible for it is acting in a clockwise direction. Similarly, any force that is believed to be acting in an anticlockwise direction will be associated with a negative torque. As the torque is influenced by the distance and force, when they seem to be larger, they give rise to a higher torque.

What happens when a dipole is placed in a non-uniform electric field?

The dipole experiences both force as well as torque when subjected to a non-uniform electric field. The dipole then aligns along the field direction, and the force experienced by the charges in the dipole is unequal; this results in a net force that acts on the dipole along the direction of the field.

When does a dipole experience a maximum electric field?

We already know that the torque on a dipole is calculated by the formula τ = P.E.sinθ. By the above expression, it is evident that the torque value will be maximum when sinθ is maximum, and this occurs when the value of θ will be 90°. So that, sin90° = 1

In how many directions does the torque wrench measure the torque?

It is known that a measurement of torque by the torque wrench is done only in one direction. A torque wrench can evaluate the torque only in a single direction as there is the possibility of only one side in which the torque wrench clicks. A torque wrench, in general, behaves simply as a normal wrench in the other direction.

Does a torque wrench tighten the rope?

Yes, a torque wrench can also be used in rope tightening by adjusting it. Firstly, we are supposed to set the weight, and the screw should be strengthened in a direction (generally clockwise direction). Then at the loop end of the rope, placement of weight is carried out, particularly at the specified position. You are said to be done when you get to hear the sound of the click.

Summary

The torque is conveniently assigned the direction using the right-hand rule, which states that the fingers in the right-hand curl along the direction that points to the radius as well as the applied force, and then the direction of torque is represented by the thumb of the right hand. Torque is a vector that is resulted when we take the cross product of the radial distance vector with the force vector.

Harshitha H N

Hi.....I am Harshitha H N. I have completed my master's in Physics from the University of Mysore with a specialization in Nuclear physics. I am well versed in the field of Latex, GAMESS software, and AVAGADRO software. I enjoy exploring new things in my free time. My article always aims to develop and bring some value to the table with relevant topics. Let’s connect through LinkedIn- https://www.linkedin.com/in/harshitha-h-n-368418249

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