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Smart Lightweight Polymer Composites
Published in Sanjay Mavinkere Rangappa, Jyotishkumar Parameswaranpillai, Suchart Siengchin, Lothar Kroll, Lightweight Polymer Composite Structures, 2020
Nayan Ranjan Singha, Mousumi Deb, Manas Mahapatra, Madhushree Mitra, Pijush Kanti Chattopadhyay
According to the Faraday’s law of induction, the magnetic field induces an electrical current, i.e., eddy current, within conductors. Notably, the eddy current suffers from the losses of heat, which is proportional to I2 × R. Here, I and R are current and resistance, respectively. For an electromagnetic radiation absorber, the eddy current loss is enhanced by increasing the thickness and electrical conductivity of the absorbing material. It is anticipated that the enhanced thickness invariably increases the traveling path length of the eddy current, leading to enhanced resistance experienced by the current, which elevates the generation of heat. Similarly, the increased conductivity augments the current flow (I), and thus, the heat loss increases. Moreover, the eddy current loss is influenced by other factors, such as orientation, grain size, surface roughness, and morphology of the absorbing material.
Electromagnetic Waves
Published in Myeongkyu Lee, Optics for Materials Scientists, 2019
Faraday’s law of induction is a basic law that predicts how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF). Faraday discovered that a time-varying magnetic flux through a conducting loop generates a current around that loop. Faraday’s law states that the EMF induced in any closed circuit is equal to the negative of the time derivative of the magnetic flux enclosed by the circuit. Let us consider a conducting wire loop C that is represented as a bold line in Figure 1.10. The magnetic flux through an open surface S bounded by the conducting loop is given by () ΦB=∫SB⋅dA⋅
Fundamentals of Magnetic Resonance I: Basic Physics
Published in Christakis Constantinides, Magnetic Resonance Imaging, 2016
The amount of nutation, or tip angle, α, away from the z axis can be changed by changing the duration or amplitude of the external magnetic field B1 (applied with a separate RF coil). A 90° pulse is known as an excitation phase, and places the magnetization on the transverse plane. Equivalently, a 180° pulse places the magnetization on the negative z axis. In general, () α=−∫0tγ.B1(t)dtFor a constant width × amplitude B1 pulse, the tip angle becomes () α=−γ.B1.Δtrf where Δtrf represents the time duration of the RF pulse in milliseconds. From Faraday’s law of induction, any changing magnetic field produces an electromotive force (EMF), which is detected as a voltage in the receiving coils. The amplitude of the induced RF voltage is minute (only of the order of a few µV), and it is amplified before being sent to the receiver for demodulation and sampling.
Power performance enhancement of vortex-induced vibration wind turbines using a semi-active control approach
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Magdy Roman, Rowida Sobh, Momtaz Sedrak, Mohamed Ali
Figure 2 shows the equivalent circuit of an electromagnetic PTO, where represents the open-circuit voltage, and are the coils resistance and inductance, respectively. Following the Faraday’s law of induction, the generated emf is proportional to the rate of magnetic field cutting, that is to say,