Magnetic Moment - Definition, Formula, Unit, Formation, Dipole Force Uses, FAQs

Otto Stern discovered the proton's magnetic moment in Hamburg in 1933. Stern was awarded the Nobel Prize for this finding in 1943. By 1934, groups led by Stern, who was now based in Pittsburgh, and I. I. Rabi of New York had measured the magnetic moments of the proton and deuteron independently.

What is a magnetic moment?

Magnetic moment is also known as magnetic dipole moment. It measures the tendency of alignment of an object in a magnetic field. When a magnet is placed in a magnetic field, it attempts to align with it. The magnet, which has a magnetic moment, is forced to a torque. This torque is used to define the magnetic moment. Magnetic moments can be found in magnets, current-carrying loops, atoms and molecules, subatomic particles, and so on.

In other words -The magnetic dipole moment, or strength of a magnetic dipole, can be regarded as a measure of a dipole's capacity to turn itself into alignment with a given external magnetic field. The magnetic dipole moment, also known as the magnetic moment, can then be defined as the greatest amount of torque induced by magnetic force on a dipole in vacuum per unit value of the surrounding magnetic field.

When considering a magnetic dipole as a current loop, the magnitude of the dipole moment is proportional to the current multiplied by the size of the enclosed region. The dipole moment's direction, which may be expressed mathematically as a vector, is perpendicular to the surface enclosed by the circular path of positive charge flow.

Magnetic moment formula:

Magnetic moment can be mathematically written as

Where,

1. m is magnetic moment

2. B is magnetic field

3. τ is torque acting of dipole

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Unit of magnetic moment

1. The si unit of magnetic moment is Amp-m²

2. We can write unit in terms of torque and magnetic field, torque is measured in Joule(J) and magnetic moment is measured in Tesla (T) and hence the unit is JT^-1

Objects having magnetic moment

The following object have magnetic moment

1. Current carrying loop

2. Electromagnet

3. Atoms and molecules

4. Permanent magnet

How is magnetic moment created

In general, the formation of the magnetic moment might have two origins. The first involves an electric and/or circular current with a current density distribution, whereas the second involves particles with their own angular momentum, known as spins.

The magnetic moment in chemistry

A dipole moment occurs in any system where there is charge separation. As a result, they can form in both ionic and covalent connections. Dipole moments develop as a result of an electronegativity mismatch between two chemically linked atoms.

A bond dipole moment quantifies the polarity of a chemical connection formed by two atoms in a molecule. It makes use of the concept of the electric dipole moment, which is a measure of the separation of negative and positive charges in a system.

The separation of positive and negative charges in a chemical is known as polar nature. Bond dipole moment is a measurement of the polar nature of a chemical bond in a molecule between two atoms. Because it has both magnitude and direction, the bond dipole moment is called a vector quantity.

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As an example,

Here + and - represents positive and negative charges Separated by d distance.

Dipole moment formula

The product of the molecule's electrical charge and the internuclear distance between its atoms may be used to define the dipole moment. The formula is as follows:

Dipole moment = Charge(Q) * distance(d)

Unit of dipole moment

The unit of dipole moment is coulomb - meter(Cm).

It is also measured in the Debye unit which is represented by D.

Dipole Moment Examples:

1. Methene (CH₃ )

2. Water (H₂O)

3. Carbon dioxide (CO₂)

4. Beryllium fluoride (BeF₂ )

5. Boron Trihydride (BH₃)

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Dipole Moment Uses:

Dipole moment is used in various fields are as follow:

1. To calculate percentage ionic character: The percentage ionic character of covalent or ionic heteronuclear diatomic compounds is calculated using dipole moment data. Consider the molecule AB, which has an observable dipole moment = obs and a bond length l cm. If the common pair is located in the middle of the atoms, the connection is completely covalent, and the percentage ionic character is zero. However, if the connection is entirely ionic and B is more electronegative than A. As a result, A has a unit positive charge and B has a unit negative charge.

2. Differentiating between cis- and trans-isomers: the isomer with the greater dipole moment is the trans-isomer, and the isomer with the lower dipole moment is the cis-isomer.

3. Dipole moment is used to find Bond angle.

4. It also assists in determining the size or structure of molecules, as well as the arrangement of chemical bonds inside them.

5. When it comes to determining the polar nature of a bond, the larger the dipole moment, the more polar the bond will be. Non-polar molecules have zero dipole moment, whereas polar molecules have a dipole moment.

6. When differentiating between ortho, meta, and para-isomers, the dipole moment of the para-isomer will be zero, while the dipole moment of the ortho-isomer will be higher than that of the meta-isomer.

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