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Question
Explain the term inductive reactance. State its unit and dimensions.
Solution
- The opposing nature of an inductor to the flow of alternating current is called inductive reactance.
- In an inductive circuit,
i0 = `"e"_0/(omega"L")` ….(1) - For a resistive ac circuit, according to Ohm’s law,
i = `"V"/"R"` ….(2)
where R = resistance in the circuit - Comparing equations (1) and (2), we can conclude that ωL plays a similar role in an inductive ac circuit as a resistor in a pure resistor circuit.
- Hence, the effective resistance XL offered by the inductance L is called inductive reactance and is given as,
XL = ωL = 2πfL. .......….(∵ ω = 2π/T = 2πf)
where f = frequency of the AC supply. - XL is directly proportional to the inductance (L) and the frequency (f) of the alternating current.
- In DC circuits, f = 0
∴ XL = 0
It implies that a pure inductor offers zero resistance to DC, i.e., it cannot reduce DC.
Thus, it passes DC and blocks AC of very high frequency. - In an inductive circuit, the self-induced emf opposes the growth as well as decay of current.
- The dimensions of inductive reactance are [ML2T-3I -2] and its SI unit is the ohm (Ω).
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