Lecture

Motion of Magnetization

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Description

This lecture covers the classical description of the motion of magnetization, viewing each spin as a magnetic dipole and analyzing the torque of a dipole in a magnetic field. It explains the Larmor equation and precession, illustrating the circular motion of the axis of a wheel with mass. The lecture also delves into rotational kinematics and the gyromagnetic ratio, providing insights into the behavior of spinning gyroscopes.

In MOOC

Fundamentals of Biomedical Imaging: Magnetic Resonance Imaging (MRI)

This physics course covers the physical principles of major in vivo bio-imaging modalities. This course will focus on magnetic resonance imaging, also known as an MRI. In the first part of the course, the dynamic of spins in a magnetic field is described, leading to the essential notions of magnetic resonance (MR), excitation and relaxation. We will also discuss the basic mechanisms of image reconstruction, MR spectroscopy and functional MRI. You will learn how existing physical principles transcend into bi

Official source

Ontological neighbourhood

Physics

Mechanics: Classical mechanics

Related concepts (32)

Circular motion

In physics, circular motion is a movement of an object along the circumference of a circle or rotation along a circular path. It can be uniform, with a constant angular rate of rotation and constant speed, or non-uniform with a changing rate of rotation. The rotation around a fixed axis of a three-dimensional body involves the circular motion of its parts. The equations of motion describe the movement of the center of mass of a body. In circular motion, the distance between the body and a fixed point on the surface remains the same.

Rotation around a fixed axis

Rotation around a fixed axis or axial rotation is a special case of rotational motion around a axis of rotation fixed, stationary, or static in three-dimensional space. This type of motion excludes the possibility of the instantaneous axis of rotation changing its orientation and cannot describe such phenomena as wobbling or precession. According to Euler's rotation theorem, simultaneous rotation along a number of stationary axes at the same time is impossible; if two rotations are forced at the same time, a new axis of rotation will result.

Larmor precession

In physics, Larmor precession (named after Joseph Larmor) is the precession of the magnetic moment of an object about an external magnetic field. The phenomenon is conceptually similar to the precession of a tilted classical gyroscope in an external torque-exerting gravitational field. Objects with a magnetic moment also have angular momentum and effective internal electric current proportional to their angular momentum; these include electrons, protons, other fermions, many atomic and nuclear systems, as well as classical macroscopic systems.

Torque

In physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). It describes the rate of change of angular momentum that would be imparted to an isolated body. The concept originated with the studies by Archimedes of the usage of levers, which is reflected in his famous quote: "Give me a lever and a place to stand and I will move the Earth". Just as a linear force is a push or a pull applied to a body, a torque can be thought of as a twist applied to an object with respect to a chosen point.

Precession

Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In other words, if the axis of rotation of a body is itself rotating about a second axis, that body is said to be precessing about the second axis. A motion in which the second Euler angle changes is called nutation. In physics, there are two types of precession: torque-free and torque-induced.

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