The Application Gallery features COMSOL Multiphysics^{®} tutorial and demo app files pertinent to the electrical, structural, acoustics, fluid, heat, and chemical disciplines. You can use these examples as a starting point for your own simulation work by downloading the tutorial model or demo app file and its accompanying instructions.

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### Electrodynamic Wheel Magnetic Levitation in 2D

This model illustrates the working principle of an electrodynamic wheel (EDW) magnetic levitation system. EDW magnetic levitation system consists of rotating and/or translationally moving permanent magnet Halbach rotor above a passive conducting guideway/track. Eddy current is induced in the guideway due to the rotation and/or translational motion of the Halbach rotor. The induced eddy ...

### Iron Sphere in a 20 kHz Magnetic Field

An iron sphere is exposed to a spatially uniform, sinusoidally time-varying, background magnetic field. The frequency of the field is such that there skin depth is smaller than the sphere radius. The induced currents in the sphere and the perturbation to the background field are computed. Proper meshing of domains with significant skin effect is addressed.

### A Geoelectrical Forward Problem

The classical forward problem of geoelectrics (includes electrical resistivity tomography, ERT and earlier techniques as vertical electric sounding, VES) is the calculation of potentials at a given set of electrodes (M,N) while current is injected at other electrodes (A,B) into the ground. Typically the physical domain (earth) is unbounded to the sides and the bottom because of which one needs ...

### Electromagnetic Force Calculation Using Virtual Work and Maxwell Stress Tensor

The model compare the electromagnetic force calculated by *virtual work* and *maxwell stress tensor* methods on the axial magntic bearing. The forces is evaluated by studying the effect of a small displacement on the electromagnetic energy of the system. This is done by using the *Magnetic Fields*, *Deformed Geometry* and *Sensitivity* physics interfaces.

### Modeling a Capacitive Position Sensor Using FEM

This tutorial model explains how to extract lumped matrices by means of the *Stationary Source Sweep* study. The capacitance matrix of a five-terminal system is used to infer the position of a metallic object similar to real-world capacitive position sensors. The example illustrates the use of FEM, which is supported by the *Electrostatics* interface. When FEM is used, a volumetric mesh of a ...

### Axisymmetric approximation of 3D Inductor

Inductive devices experience capacitative coupling between conductors at high frequencies. Modeling this phenomenon requires that you describe electric fields that have components both parallel with and perpendicular to the wire. This consideration might lead to the conclusion that a 3D model is always necessary to model the phenomenon, even if the coil is a helix, which is actually not the ...

### Self-Demagnetization of a Cylindrical AlNiCo Magnet

Soft permanent magnets like AlNiCo are easily demagnetized if handled incorrectly. This is a demonstration of how to model the self-demagnetization of a cylindrical AlNiCo magnet when moved out of its associated/protective magnetic circuit. The modeling is performed in three steps: 1. The soft magnet protected by the magnetic circuit. 2. The self-demagnetization of the soft magnet when moved ...

### Iron Sphere in a 13.56 MHz Magnetic Field

An iron sphere is exposed to a spatially uniform, sinusoidally time-varying, background magnetic field. The frequency of the field is so high that the skin depth in the sphere is much smaller than the radius. At such high frequencies it is possible to model only the fields and induced currents on the surface of the sphere, thus avoiding the need for solving for the fields within the volume of ...

### Comparison of Effective H-B/B-H Curve with Linear and Nonlinear Material Models

This example illustrates how to set up the effective H-B/B-H curve material model, introduced in COMSOL Multiphysics® version 5.2, for modeling magnetic materials in the frequency domain. The model also compares the results from the effective H-B/B-H curve model with the linear and nonlinear H-B/B-H curve material model in 2D.

### Operational Amplifier with Capacitive Load

An operational amplifier (op-amp) is a differential voltage amplifier with a wide range of applications in analog electronics. This tutorial models an op-amp connected to a feedback loop and a capacitive load. The op-amp is modeled as an equivalent linear subcircuit in the *Electrical Circuit* interface, where it is inserted into an outer circuit. The model is partially based on the SPICE ...