BlogNCERTCurrent Loop and Magnetic Dipole Moment

Current Loop and Magnetic Dipole Moment


In motors, the magnetic force on current-carrying wires is the most prevalent method. Motors have wire loops in a magnetic field. When electricity is passed through the loops, the magnetic field exerts stress on them, rotating a shaft.

    Fill Out the Form for Expert Academic Guidance!


    Live ClassesBooksTest SeriesSelf Learning

    Verify OTP Code (required)

    I agree to the terms and conditions and privacy policy.

    Electrical energy is converted into mechanical work during this procedure. After the loop’s surface area is aligned with the magnetic field, the current direction is reversed, resulting in a constant torque on the loop. To reverse the current flow, commutators and brushes are utilized.

    The commutator is configured to reverse the current flow at key points to keep the motor running. There are three contact places to avoid on a simple commutator, as well as dead spots where the loop would have zero resistance. The twisting force that causes rotation is known as torque.

    A current loop is an electrical system that sends signals to a device using two wires. It can be used to provide electricity or for analogue signalling. The power supply’s current goes through the wire to the transmitter. The current flow is controlled by the transmitter.

    The loop current, which is proportional to the measured parameter, is the only current allowed to travel through the transmitter. Through the wire, the current returns to the controller.

    The information about current loop and magnetic moment from various physics-related articles are available here. Current loop and its general concepts are important topics in physics. Students who want to flourish in physics need to be well known about the current loop to get deep knowledge about it to do well on their exams. The general ideologies, and concepts related to magnetic dipole moment are provided here to assist students in effectively understanding the respective topic. Continue to visit our website for additional physics help.


    The term “magnetic moment” usually refers to a system’s magnetic dipole moment, which is the component of the magnetic moment that can be represented by the same magnetic dipole: magnetic north and south poles separated by a little distance.

    For tiny enough magnets or long enough distances, the magnetic dipole component is sufficient. For longer objects, higher-order formulas (such as the magnetic quadrupole moment) may be required in addition to the dipole moment.

    The magnetic moment is a measurement of a magnet’s magnetic strength and orientation, as well as any other item that produces a magnetic field. A magnetic moment is more properly referred to as a magnetic dipole moment, which is the component of the magnetic moment that can be represented by a magnetic dipole.

    A magnetic dipole is made up of two magnetic north poles separated by a little distance. Magnetic dipole moments have dimensions equal to current times area or energy divided by magnetic flux density. In meter–kilogram–second–ampere, the dipole moment is measured in ampere-square metre.

    The erg (unit of energy) per gauss is the unit in the centimetre–gram–second electromagnetic system (unit of magnetic flux density).

    The magnetic dipole moment of an object or phenomenon can be easily calculated in terms of the torque it experiences in a magnetic field. On objects with larger magnetic moments, the same applied magnetic field generates larger torques.

    The direction and strength of this torque are determined not only by the magnetic moment’s degree but also by its placement in relation to the magnetic field’s direction. As a result, the magnetic moment can be thought of as a vector.

    Derivation of Magnetic Dipole Moment Formula:

    The magnetic field, B due to a current loop carrying a current i having a radius R at a distance l along its axis is,

    B=μ0iR2 /2(R²+l²)3/2

    Now, when we consider a point very far from the current loop such that ∣>>R, then we can easily approximate the field as,

    B=μ0iR2 2[l³(R/l)²+1]3/2 ≈ μ0iR2 2l³ ≡ μ02i πR² /4πl³

    Then, the area of the loop A is,


    Therefore, the magnetic field will be,

    B=μ02i A /4πl³


    We can represent this new quantity as a vector that points along the magnetic field.


    We have,

    E=(1/4πε0 ) (2p/r³ )

    Therefore, we can call this quantity the magnetic dipole moment.

    In general, magnetic fields do not have ‘charge’ equivalents. In other words, there can only be a dipole because there are no magnetic field sources or sinks. Anything capable of producing a magnetic field has both a source and a sink, i.e. a north pole and a south pole.

    The magnetic dipole is the fundamental unit that can generate a magnetic field in many ways. Most of the elementary substances or particles are magnetic dipoles by nature. The electron, for example, possesses a Spin Magnetic Dipole moment and behaves like a magnetic dipole.

    Because the electron has no area A (it is a point object) and does not rotate about itself, its magnetic moment is intrinsic to the nature of the electron’s existence.

    In general, the magnetic moment for ‘ N ‘ turns of the wire loop is,


    Magnetic Dipole Moment of a Current Loop:

    We have the magnitude m of the magnetic dipole moment of a current loop carrying current I with area A.

    So, the magnetic dipole moment will be,


    The magnetic dipole moment has a direction that is perpendicular to the plane of the current loop.

    Also read: Important Topic of Physics: Faraday’s Law

    Frequently Asked Question (FAQs):

    Question 1: What is the magnetic dipole behaviour of an atom?

    Answer: Electrons in an atom are restricted to a constrained orbit around the nucleus. The orbit of electrons around the nucleus resembles a current loop because they are charged particles. The electrons spin in the opposite direction to the current, which spins in the opposite direction.

    The development of a south pole and a north pole by electron migration causes the atom to act like a magnetic dipole. These effects may cancel out, making it impossible for a specific sort of atom to be a magnetic dipole. If they do not cancel, the atom, like iron atoms, has a permanent magnetic dipole.

    Millions of iron atoms have spontaneously latched onto the same alignment to form a ferromagnetic domain, forming a magnetic dipole. Magnetic compass needles and bar magnets are examples of macroscopic magnetic dipoles.

    Question 2: What do you mean by a Magnetic Dipole?

    Answer: When the size of a closed loop of electric current or a pair of poles is reduced to zero while the magnetic moment remains constant, the result is a magnetic dipole. Although it isn’t a perfect match, it is a magnetic analogue of the electric dipole.

    In nature, there has never been an actual magnetic monopole, which is the magnetic equivalent of an electric charge. Magnetic monopole quasiparticles, on the other hand, have been found as emergent properties in a variety of condensed matter systems. One sort of magnetic dipole moment is also linked to a fundamental quantum property: elementary particle spin.

    Question 3: What do you mean by a Magnetic Dipole Moment?

    Answer: The magnetic dipole moment, also known as the strength of a magnetic dipole, is a measurement of a dipole’s ability to align itself with a specific external magnetic field. The highest amount of torque given to the dipole, which happens when the dipole is at right angles to the magnetic field, determines the size of the dipole moment in a uniform magnetic field.


    Chat on WhatsApp Call Infinity Learn

      Talk to our academic expert!


      Live ClassesBooksTest SeriesSelf Learning

      Verify OTP Code (required)

      I agree to the terms and conditions and privacy policy.