SI unit of Resistance | What is the SI unit of Resistance
- Ohm
Hello dear students we all know that, the ability of metal wire of carrying electric current depends upon the number of free electrons present in the given material. The motion of electrons inside the metal wire is restricted or obstructed by neighbouring electrons. Due to this the every electron has an opposition for its flow inside conductor. This opposition is known as resistance. The sum of opposition provided by individual electric component is termed as impedance.
George Ohm, German physicist studied the variation of potential difference and electric current and stated the most important law in electricity, known as Ohm’s law. According to this law, “if the physical state of conductor (length, area of cross section, material and temperature) remains the same, electric current (I) flowing through the conductor is directly proportional to potential difference (V) across the terminals of conductor”.
Then we can write,
∴ V α I
∴ V = I R
Where, R is constant, called as reistance.
∴ R = V/I
According to formula, SI unit of resistance can be volt per ampere.
Considering the contribution of George Ohm, SI unit of resistance is named after him as ‘ohm’.
From the formula, SI unit of resistance should be,
∴ SI unit of R = volt/ampere
volt/ampere is then renamed as ohm.
Hence, SI unit of resistance is then taken as ‘ohm’. Its symbol is ‘Ω’
(1 volt)/(1 ampere) = 1 ohm
i.e. when 1 volt of potential difference across the terminals of wire sends current of 1 ampere, the resistance of wire is said to be 1 ohm.
Ohm is also taken as unit for inductive reactance, capacitive reactance and impendence in the circuit.
Important Faq
Q.1) On which factors the resistance of conductor depends?
Answer: Resistance of conductor depends upon length of conductor, area of cross section of conductor, temperature of conductor an material of conductor.
Q.2) What is the name of device used for offering external resistance?
Answer: Resistor is a device used for offering external resistance in electric circuit. Devices like resistance box, rheostat are also used to offer variable resistance in electric circuit.
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