What is Torque?

Torque is a measure of the twisting force applied to an object. It is defined as the product of the force applied to an object and the perpendicular distance from the axis of rotation to the point where the force is applied.

Understanding Torque

Torque is a vector quantity, which means that it has both magnitude and direction. The magnitude of torque is measured in newton-meters (N·m) or pound-feet (lb·ft). The direction of torque is determined by the right-hand rule.

Calculating Torque

The formula for calculating torque is:

$$ τ = F × r $$

where:

• τ is torque (N·m or lb·ft)
• F is the force applied to the object (N or lb)
• r is the perpendicular distance from the axis of rotation to the point where the force is applied (m or ft)

Examples of Torque

Here are some examples of torque:

• When you turn a screw, you are applying torque to the screw. The force you apply to the screwdriver is multiplied by the length of the screwdriver to create torque.
• When you open a door, you are applying torque to the door. The force you apply to the doorknob is multiplied by the distance from the doorknob to the hinges to create torque.
• When a car engine is running, the pistons are applying torque to the crankshaft. The force of the pistons is multiplied by the length of the connecting rods to create torque.

Applications of Torque

Torque is used in a wide variety of applications, including:

• Automotive: Torque is used to measure the power of car engines. The higher the torque, the more powerful the engine.
• Industrial: Torque is used to power machines such as cranes, forklifts, and conveyor belts.
• Construction: Torque is used to tighten bolts and screws.
• Sports: Torque is used to measure the power of athletes. For example, a baseball player’s torque is measured by the speed of their bat swing.

Torque is a fundamental concept in physics that has a wide range of applications. By understanding torque, you can better understand how the world around you works.

What is an Electric Dipole?

Electric Dipole

An electric dipole is a pair of equal and opposite charges separated by a small distance. The dipole moment is a vector quantity that points from the negative charge to the positive charge and has a magnitude equal to the product of the magnitude of one of the charges and the distance between them.

Properties of Electric Dipoles

• Electric dipoles create electric fields. The electric field of an electric dipole is proportional to the dipole moment and inversely proportional to the cube of the distance from the dipole.
• Electric dipoles can be induced in materials. When a material is placed in an electric field, the charges in the material can be displaced, creating an electric dipole. This process is called polarization.
• Electric dipoles interact with each other. The interaction between two electric dipoles is proportional to the product of the dipole moments of the two dipoles and inversely proportional to the cube of the distance between them.

Applications of Electric Dipoles

Electric dipoles are used in a variety of applications, including:

• Antennas: Electric dipoles are used as antennas to transmit and receive electromagnetic waves.
• Capacitors: Electric dipoles are used in capacitors to store electrical energy.
• Electrets: Electrets are materials that have a permanent electric dipole moment. They are used in a variety of applications, such as microphones, speakers, and sensors.

Electric dipoles are a fundamental concept in electromagnetism. They have a variety of properties and applications, and they play an important role in our understanding of the world around us.

Torque on a Dipole in a Uniform Electric Field

A dipole consists of two equal and opposite charges separated by a small distance. When a dipole is placed in a uniform electric field, it experiences a torque that tends to align it with the field.

Calculation of Torque

The torque on a dipole in a uniform electric field is given by the following equation:

$$\tau = pE\sin\theta$$

where:

• $\tau$ is the torque in newton-meters (N$\cdot$m)
• $p$ is the dipole moment in coulomb-meters (C$\cdot$m)
• $E$ is the electric field strength in volts per meter (V/m)
• $\theta$ is the angle between the dipole moment and the electric field

Explanation of the Equation

The torque on a dipole is caused by the interaction between the electric field and the charges of the dipole. The electric field exerts a force on each of the charges, and these forces create a net torque that tends to rotate the dipole.

The magnitude of the torque is proportional to the dipole moment and the electric field strength. The dipole moment is a measure of the strength of the dipole, and the electric field strength is a measure of the strength of the electric field.

The angle between the dipole moment and the electric field also affects the magnitude of the torque. The torque is greatest when the dipole moment is perpendicular to the electric field, and it is zero when the dipole moment is parallel to the electric field.

Applications of Torque on a Dipole

The torque on a dipole is used in a variety of applications, including:

• Electric motors: Electric motors use the torque on a dipole to convert electrical energy into mechanical energy.
• Magnetic compasses: Magnetic compasses use the torque on a dipole to align themselves with the Earth’s magnetic field.
• Electron microscopes: Electron microscopes use the torque on a dipole to focus the electron beam.

The torque on a dipole in a uniform electric field is a fundamental concept in electromagnetism. It has a variety of applications, including electric motors, magnetic compasses, and electron microscopes.

Solved Examples on Torque on a Dipole

Example 1: Calculating Torque on a Dipole in a Uniform Electric Field

Consider a dipole consisting of two equal and opposite charges, +q and -q, separated by a distance 2a. The dipole is placed in a uniform electric field of strength E. The dipole moment of the dipole is given by:

$$p = 2qa$$

The torque acting on the dipole is given by:

$$\tau = pE\sin\theta$$

where $\theta$ is the angle between the dipole moment and the electric field.

If the dipole is aligned parallel to the electric field, then $\theta = 0$ and the torque is zero. If the dipole is aligned perpendicular to the electric field, then $\theta = 90^\circ$ and the torque is maximum.

In this example, let’s assume that the dipole is aligned at an angle of $30^\circ$ to the electric field. Then, the torque acting on the dipole is:

$$\tau = (2qa)E\sin30^\circ = qaE$$

Example 2: Calculating the Work Done in Rotating a Dipole in a Uniform Electric Field

Consider the same dipole as in Example 1. We want to calculate the work done in rotating the dipole from an initial angle of $\theta_1 = 0^\circ$ to a final angle of $\theta_2 = 90^\circ$.

The work done in rotating the dipole is given by:

$$W = -\int_{\theta_1}^{\theta_2} \tau d\theta$$

Substituting the expression for torque, we get:

$$W = -\int_{\theta_1}^{\theta_2} pE\sin\theta d\theta$$

Integrating, we get:

$$W = -pE\left[\cos\theta\right]_{\theta_1}^{\theta_2}$$

Substituting the values of $\theta_1$ and $\theta_2$, we get:

$$W = -pE(\cos90^\circ - \cos0^\circ) = pE$$

Therefore, the work done in rotating the dipole from $0^\circ$ to $90^\circ$ is equal to the dipole moment times the electric field strength.

Example 3: Calculating the Potential Energy of a Dipole in a Uniform Electric Field

The potential energy of a dipole in a uniform electric field is given by:

$$U = -\overrightarrow{p}\cdot\overrightarrow{E}$$

where $\overrightarrow{p}$ is the dipole moment and $\overrightarrow{E}$ is the electric field.

If the dipole is aligned parallel to the electric field, then the potential energy is minimum. If the dipole is aligned perpendicular to the electric field, then the potential energy is maximum.

In this example, let’s assume that the dipole is aligned at an angle of $30^\circ$ to the electric field. Then, the potential energy of the dipole is:

$$U = -(2qa)E\cos30^\circ = -qaE$$

Therefore, the potential energy of the dipole is equal to the negative of the dipole moment times the electric field strength.

Torque On A Dipole FAQs

What is torque on a dipole?

Torque on a dipole is the force that causes a dipole to rotate. It is defined as the cross product of the dipole moment and the electric field.

What is the formula for torque on a dipole?

The formula for torque on a dipole is:

$$ τ = p × E $$

where:

• τ is the torque (in newton-meters)
• p is the dipole moment (in coulomb-meters)
• E is the electric field (in volts per meter)

What is the direction of torque on a dipole?

The direction of torque on a dipole is perpendicular to both the dipole moment and the electric field. It is given by the right-hand rule.

What are some examples of torque on a dipole?

Some examples of torque on a dipole include:

• The torque on a bar magnet in a magnetic field
• The torque on an electric dipole in an electric field
• The torque on a spinning top in a gravitational field

What are the applications of torque on a dipole?

Torque on a dipole has a number of applications, including:

• Motors and generators
• Magnetic resonance imaging (MRI)
• Particle accelerators
• Mass spectrometers

Conclusion

Torque on a dipole is a fundamental concept in physics that has a wide range of applications. By understanding the basics of torque on a dipole, you can better understand how the world around you works.