Maharashtra BoardEnglish MediumSTD 12 SciencePhysicsQuestion Bank [ 2022 ]3 Marks
Question
Explain the term inductive reactance. State its unit and dimensions.
✓
Answer
i. The opposing nature of an inductor to the flow of alternating current is called inductive reactance. ii. In an inductive circuit, $ i _0=\frac{ e _0}{\omega L } \text {... } $ iii. For a resistive ac circuit, according to Ohm's law, $ i =\frac{ V }{ R } \text {. } $ where $R =$ resistance in the circuit iv. Comparing equations (1) and (2), we can conclude that $\omega L$ plays a similar role in an inductive ac circuit as a resistor in a pure resistor circuit. $v$. Hence, the effective resistance $X_L$ offered by the inductance $L$ is called inductive reactance and is given as, $ X_L=\omega L=2 \pi f L . \ldots \ldots \ldots \ldots .(\because \omega=2 \pi / T=2 \pi f) $ where $f=$ frequency of the AC supply. vi. $X_L$ is directly proportional to the inductance $(L)$ and the frequency (f) of the alternating current. vii. In DC circuits, $f=0$ $ \therefore X _{ L }=0 $ It implies that a pure inductor offers zero resistance to $D C$, i.e., it cannot reduce $D C$. Thus, it passes DC and blocks AC of very high frequency. viii. In an inductive circuit, the self-induced emf opposes the growth as well as decay of current. ix. The dimensions of inductive reactance are $\left[ ML ^2 T ^{-3} I ^{-2}\right]$ and its SI unit is the ohm $(\Omega)$.
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