Impedance
Impedance (Z)
Impedance (pronounced: im-PEE-dans) is a term used in Physics and Engineering to describe the measure of the opposition that a circuit presents to a current when a voltage is applied. In the field of Biomedical Engineering, it is often used to refer to the resistance of body tissues to the flow of electric current.
Etymology
The term "Impedance" is derived from the Latin word "impedire" which means to hinder or obstruct. It was first used in this context in the late 19th century.
Definition
In Electrical Engineering, impedance is a complex quantity that measures how much a circuit resists the flow of electric current for a given voltage. It is denoted by the symbol Z and is measured in ohms (Ω).
In Medicine
In Medicine, impedance is used in various diagnostic and therapeutic procedures. For example, in Electrocardiography, impedance is used to measure the electrical activity of the heart. Similarly, in Bioimpedance Analysis, it is used to estimate body composition and fluid shifts.
Related Terms
- Resistance: In electrical circuits, resistance is the opposition to current flow, measured in ohms. In the context of impedance, resistance is the real part of impedance.
- Reactance: Reactance is the imaginary part of impedance, representing the amount of opposition to a change in electric current or voltage.
- Ohm: The unit of measure for impedance and resistance.
- Electrocardiography: A medical test that measures the electrical activity of the heart.
- Bioimpedance Analysis: A method used in medicine to estimate body composition and fluid shifts.
External links
- Medical encyclopedia article on Impedance
- Wikipedia's article - Impedance
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