resistance


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Related to resistance: voltage, electrical resistance, resistor

resistance,

property of an electric conductor by which it opposes a flow of electricity and dissipates electrical energy away from the circuit, usually as heat. Optimum resistance is provided by a conductor that is long, small in cross section, and of a material that conducts poorly. Resistance is basically the same for alternating and direct current circuits (see impedanceimpedance,
in electricity, measure in ohms of the degree to which an electric circuit resists the flow of electric current when a voltage is impressed across its terminals.
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). However, an alternating current of high frequency tends to travel near the surface of a conductor. Since such a current uses less of the available cross section of the conductor than a direct current, it meets with more resistance than a direct current. In circuit analysis an ideal resistorresistor,
two-terminal electric circuit component that offers opposition to an electric current. Resistors are normally designed and operated so that, with varying levels of current, variations of their resistance values are negligible (see resistance).
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, i.e., a circuit component whose only property is resistance, is called a resistance. The phenomenon of resistance arises from the interactions of electrons with ions in the conductor. The unit of resistance is the ohmohm
[for G. S. Ohm], symbol Ω, unit of electrical resistance, defined as the resistance in a circuit in which a potential difference of one volt creates a current of one ampere; hence, 1 ohm equals 1 volt/ampere. The megohm (1,000,000 ohms) and the milliohm (.
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. See superconductivitysuperconductivity,
abnormally high electrical conductivity of certain substances. The phenomenon was discovered in 1911 by Heike Kamerlingh Onnes, who found that the resistance of mercury dropped suddenly to zero at a temperature of about 4.
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; Ohm's lawOhm's law
[for G. S. Ohm], law stating that the electric current i flowing through a given resistance r is equal to the applied voltage v divided by the resistance, or i=v/r.
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; conductionconduction,
transfer of heat or electricity through a substance, resulting from a difference in temperature between different parts of the substance, in the case of heat, or from a difference in electric potential, in the case of electricity.
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.

resistance,

in biology: see immunityimmunity,
ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian immunity.
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.

resistance,

in psychiatry: see psychoanalysispsychoanalysis,
name given by Sigmund Freud to a system of interpretation and therapeutic treatment of psychological disorders. Psychoanalysis began after Freud studied (1885–86) with the French neurologist J. M.
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.

Resistance

The physical property of a material to resist or impede the conduction of electrical current, measured in ohms. High resistance means poor conductivity and vice versa.

resistance

[ri′zis·təns]
(acoustics)
(electricity)
The opposition that a device or material offers to the flow of direct current, equal to the voltage drop across the element divided by the current through the element. Also known as electrical resistance.
In an alternating-current circuit, the real part of the complex impedance.
(fluid mechanics)
(mechanics)
In damped harmonic motion, the ratio of the frictional resistive force to the speed. Also known as damping coefficient; damping constant; mechanical resistance.

electrical resistance

The physical property of a device, conductor, element, branch, or system, by virtue of which power is lost as heat when current flows through it; the physical property which an electric conductor exhibits to the flow of current; measured in ohms.

resistance

1. 
a. the opposition to a flow of electric current through a circuit component, medium, or substance. It is the magnitude of the real part of the impedance and is measured in ohms.
b. (as modifier): resistance coupling
2. any force that tends to retard or oppose motion
3. (in psychoanalytical theory) the tendency of a person to prevent the translation of repressed thoughts and ideas from the unconscious to the conscious and esp to resist the analyst's attempt to bring this about
4. Physics the magnitude of the real part of the acoustic or mechanical impedance
References in periodicals archive ?
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One possible way to minimize both lipodystrophy and cross resistance is for somebody to start on d4T for perhaps six months, then switch over to tenofovir once their viral load is clearly less than 50 copies, for example.
I hear this quite often: "If you move a resistance slow, you'll only become slow.
After your warm-up period, use the gears of the bike or the resistance feature of the computer on the club's stationary bike to increase the resistance and bring your heart rate up to your target beats per minute.
The latest drug resistance rates obtained from Chest Hospital, a specialized TB referral hospital, showed that the combined drug resistance of any and multiple drugs were 27.