Thoracic impedance change equation deduced on the basis of parallel impedance model and Ohm's law

Xiao Qiu-Jin1, Wang Zhen, Kuang Ming-Xing

  • 1Department of Special Diagnosis, 94th Hospital of People's Liberation Army of China, Jiangxi Nanchang, China.

Medical Physics
|February 11, 2012
PubMed
Abstract

Related Concept Videos

Impedance Combination01:21

Impedance Combination

Consider a string of christmas lights, each bulb symbolizing an impedance element. In this series configuration, the flow of electric current remains uniform across every component. This behavior aligns with Kirchhoff's Voltage Law (KVL), which asserts that the total impedance in such a setup equals the sum of individual impedances—akin to resistors in series. It follows that the voltage from the power source is distributed proportionally among these components, adhering to the voltage division...
Ohm's Law01:19

Ohm's Law

Resistors are fundamental components in electrical circuits, often manufactured from metallic alloys or carbon compounds. They model a material's ability to resist the flow of electric current, a characteristic that is crucial in controlling and regulating electrical power within a circuit.
This current-resisting behavior of resistors is governed by Ohm's law, which states that the voltage across a resistor is directly proportional to the current flowing through it.
Ohm's Law01:21

Ohm's Law

Many materials exhibit a simple relationship between the values of current, voltage, and resistance, known as Ohm’s law. The current that flows through most substances is directly proportional to the voltage applied to them. The German physicist Georg Simon Ohm (1787–1854) was the first to demonstrate experimentally that the current in a metal wire is directly proportional to the voltage applied. Any material, component, or device that obeys Ohm’s law, where the current through the device is...
Current Dividers01:10

Current Dividers

In parallel electrical connections, resistors are linked between the same pair of nodes, creating an equal voltage across each resistor. Kirchhoff's current law is applied to these connections, establishing that the sum of currents through these resistors equals the source current. Utilizing Ohm's law, the source current is determined as the product of the source voltage and the sum of the reciprocals of individual resistances. This relationship simplifies the process of finding the current...
RLC Series Circuits: Impedance01:29

RLC Series Circuits: Impedance

When current flow is opposed in a DC or AC circuit, it is referred to as resistance or impedance, respectively. Impedance plays a key role in determining the performance of AC circuits. It is represented by Z, which is a combination of resistance and reactance, and depends upon the angular frequency, measured in ohms.
Thus, the magnitude of the impedance is given by the following equation,
Series Impedances: Three-Phase Line01:27

Series Impedances: Three-Phase Line

Calculating series impedances for a three-phase overhead line involves evaluating resistances and inductive reactances in a network with three-phase and multiple neutral conductors grounded at regular intervals.
Using Kirchhoff's laws, an integro-differential equation for the network is derived. This equation accounts for unbalanced phase currents, which may induce return currents through neutral wires and the earth, seeking the least impedance path. Earth return conductors can replace the...