# Application Gallery

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.

Search for tutorials and apps relevant to your area of expertise via the Quick Search feature. To download the MPH-files, log in or create a COMSOL Access account that is associated with a valid COMSOL license. Note that many of the examples featured here can also be accessed via the Application Libraries that are built into the COMSOL Multiphysics® software and available from the File menu.

### Transient Modeling of a Capacitor in a Circuit

A transient model of a capacitor is solved in combination with an external electrical circuit. The finite element model of the capacitor is combined with a circuit model of a voltage source and a resistor. A step change in voltage is applied, and the transient current through the capacitor is computed and compared to the analytic result.

### Modeling of an Electric Generator in 3D

These models demonstrate how to setup a sector model of rotating machinery both in 2D and 3D using *Rotating Machinery, Magnetic* interface in COMSOL Multiphysics. The stator in these permanent magnet ac generator examples consists of stator winding backed by iron core. The rotor includes the permanent magnets and iron core. The 2D and 3D model of the generator are included here. In 2D, the ...

### Permanent Magnet Motor in 3D

Permanent magnet (PM) motors are used in many high-end applications, such as in electric and hybrid vehicles. An important design limitation is that the magnets are sensitive to high temperatures, which can occur through heat losses caused by currents, particularly eddy currents. In this tutorial, an 18-pole PM motor is modeled in 3D to accurately capture eddy current losses in the magnets. ...

### Frequency Domain Modeling of a Capacitor

A capacitor with an applied sinusoidally time-varying voltage difference is modeled. A wide frequency range is considered and the impedance of the device is computed. Solver accuracy is addressed. The relationship between the frequency domain impedance and the steady-state capacitance and resistance of the device is discussed.

### Electromagnetic Forces on Parallel Current-Carrying Wires

This model shows a setup of two parallel wires with a constant current running through both. Their cross-sections are successively reduced until a set force per unit length is reached.

### Multi-Turn Coil Above an Asymmetric Conductor Plate

This model solves the Testing Electromagnetic Analysis Methods (TEAM) problem 7, “Asymmetrical Conductor with a Hole”—a benchmark problem concerning the calculation of eddy currents and magnetic fields produced when an aluminum conductor is placed asymmetrically above a multi-turn coil carrying a sinusoidally varying current. The simulation results at specified positions in space are compared ...

### Computing the Resistance of a Wire

Every electrical device has some resistance. That is, when a voltage difference is applied across any two terminals of the device, there will be a directly proportional current flow. This model demonstrates how to compute the resistance of a short section of copper wire. The convergence of the solution with respect to the mesh size is also studied.

### Magnetic Brake

A magnetic brake consists of a permanent magnet, which induces currents in a rotating copper disk. The resulting eddy currents interact with the magnetic flux to produce Lorentz forces and subsequently a braking torque. This 3D problem is solved using a stationary formulation for the electromagnetic field coupled to an ordinary differential equation for the rotational rigid body dynamics. ...

### Integrated Square-Shaped Spiral Inductor

This model considers a square inductor that is used for LC bandpass filters in MEMS systems. The simulation calculates the self-inductance. The first step in the modeling is to compute the currents in the inductor. These currents are the source for the magnetic flux computations, carried out in a second step.

### Magnetic Lens

A scanning electron microscope samples images by scanning a target with a high-energy beam of electrons. The subsequent electron interactions produce signals such as secondary and back-scattered electrons that contain information about the sample surface topography. Electromagnetic lenses are used to focus this electron beam down to a spot about 10 nm wide on the sample surface. This model ...

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