Wednesday, May 4, 2011

RESISTANCE AND UNIT OF RESISTANCE - OHM

Resistance: "The flow of electrons through a conductor is opposed by the conductor. Since this flow of electrons constitutes a current, the flow of a current is offered opposition by the conductor. This property of the conductor due to which it opposes or resists the flow of electrons is called Resistance."

A device whose chief property is to oppose or resist is called Resistor. And If the opposition is variable, the device is called a variable resistance or a Rheostat.

The unit of Resistance is ohm (𝛺) and it is pronounced as omega.

A conductor is said to offer a resistance of 1 ohm, when it allows a current of 1 ampere to flow through it when 1 volt of potential is applied across its terminals.

When the resistances are too high (e.g., for insulators) to be measured in ohms, one may employ the unit kilo-ohms (K𝛺) or mega-ohms (M𝛺). If the resistances are very small (less than an ohm), units such as milli ohm (10⁻³ 𝛺) or micro-ohm (10⁻⁶ 𝛺) are used.

In an electrical formula, the letter "R" generally stands for the resistance of a conductor.

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