What is electrical resistance how does resistance affect current ? | what is resistance unit ?
There are 3 basic components of electrical Resistance , Inductor , Capacitor.
All electrical machine, equipment, circuits are basically different combination of this basic component.
What is electrical resistance ?
Definition:
Resistance is a property of electrical conductor to oppose the flow of electrical current passing through it.
Different material have different specific resistance depending on its atomic structure.
Sign if resistance is R and its unit is ohm Ω .
Symbol of resistance is
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| Symbol of resistance |
Laws of resistance:
The resistance R offered by a conductor depends on the following factors.
• The resistance of the conductor varies directly with its length.
• The resistance of the conductor is inversely proportional to its cross-sectional area.
• The resistance of the conductor depends on the material with which it is made of.
• It also depends on the temperature of the conductor.
Ignoring the last factor temperature for the time being,
we can say
where ,
ρ is resistivity of material
L length of conductor
a is cross section area of conductor
If resistivity of material high, Resistance of that material is high. for example resistivity of aluminum is higher than copper. so specific resistance of copper is lower than that of aluminum.
If length of conductor is increases , resistance is also increases.
Cross section area is inversely proportional with resistance so if area of conductor increase resistance also increases.
How to measure resistance ?
Ohmic value of a small and medium resistance is measured by an ohmmeter or a Wheatstone bridge. There is a provision to measure the ohmic value of a resistance in a multimeter.
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