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resistance
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Resistance
Resistance and reactance are terms from physics which are part of
the complex field of materials and their effects on electricity.
However, in reality, resistance and reactance are easy to understand.
Resistance is the ratio of electrical potential (voltage) to the
current in a material. Simply put, a material with high resistance
requires a high potential to generate a given amount of current in
the material. A material with low resistance requires a low potential
to generate the same amount of current.
Perhaps the easiest way to think about this is to say that a material
with low resistance conducts well, while a material with high resistance
conducts poorly.
Steel, which conducts well, is said to have low resistance. Wood
which conducts poorly, is said to have high resistance. Because of
its electrolyte (charged ion) content, salt water conducts well and
has low resistance, while pure water conducts poorly and is said
to have high resistance.
When a material is conducting, it releases energy in the form of
heat. Therefore, the resistance of a material is related to the material's
ability to dissipate energy. Units of resistance are called ohms.
In the human body, low resistance is associated with large amounts
of lean body weight (or fat-free mass). High resistance is associated
with smaller amounts of lean body weight.
 Why
is this the case?
The primary conductor in the human body is ionized water. As the
percentage of body weight that is water increases, the conductivity
of the body increases. Since body water is contained solely within
lean body weight, the conductivity of the body is proportional to
the amount of lean body weight.
How is resistance measured?
A small current is applied through the body. The potential required
to generate the current is measured. The ratio of potential and current
along with a process called correlation and integration are used
to determine the resistance and reactance respectively.
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