RESISTANCE
Resistance
is the physical property of any electrical circuit, whose opposes the flow of
electric current. Measured in ohms, symbolized by thee Greek letter Ω (ohm). Invented by Georg simon ohm he is a German physicist.
Resistance denoted by “R”.
Resistance is a constant or proportional term found by relation of voltage with current by ohm’s law.
( voltage is direct proportional of current )
V = Ri ( if we remove the proportional term and
therefore the constant term R put in this equation )
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FACTOR GOVERNING THE
RESISTANCE
(1) Type and nature
of material :- Every material has different resistance depending
on the availability of free electrons. Silver is good conductor of
electricity where as iron has high resistance material in there pure
form have minimum resistance in the hardness ( due to heat treatment ).
(2) Length of the
conductor
:- resistance of the conductor is
directly proportional to its length.
(3) Cross sectional
area :-
Resistance of the conductor is inversely proportional to area of the conductor.
(4) Temperature :- In most
material resistance increases with the temperature.
SPECIFIC RESISTANCE OR
RESISTIVITY
Resistivity
is physical property of any material which can define the how strongly can the
material opposes the flow of electric current. In another word Specific resistance is defined as the resistance offered per
unit length and unit cross-sectional area when a known amount of voltage is
applied. The mathematical representation is as follows:
The
S.I unit of resistivity is ohm-meter . denoted by sigma (
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| STUDYWALLE |
TYPE’S
OF RESISTANCE
Resistance
classified into three parts.
LOW RESISTANECE :- Resistance upto and including one
ohm are known as low resistance. (
MEDIUM RESISTANCE :- All
resistance from one ohm upwards to about 0.1 mega ohm are known as medium
resistance. ( 1 < R < 100kΩ )
HIGH RESISTANCE :- Resistances above 0.1 mega ohm are
known as high resistance. ( 100kΩ < R )
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