This question was previously asked in

ESE Electrical 2016 Paper 1: Official Paper

Option 1 : 33.20

CT 3: Building Materials

2962

10 Questions
20 Marks
12 Mins

**Concept:**

As the bandwidth is taken between the two -3dB points, the selectivity of the circuit is a measure of its ability to reject any frequencies either side of these points. A more selective circuit will have a narrower bandwidth whereas a less selective circuit will have wider bandwidth.

The quality factor is the measure of selectivity. Mathematically, **Selectivity** is** **given as.

\({S} = {{f_0}\over |BW|}\)

\(S = {Q}\)

under resonance condition, the voltage across the L & C components are Q times the supply voltage. Hence, the series RLC circuit is considered as the **voltage amplification circuit**.

V_{L} = Q × V_{s}

At resonance, the quality factor is given by

\(Q = \frac{{\omega L}}{R} = \frac{{{V_L}}}{{{V_S}}}\)

\(S = \frac{{{V_L}}}{{{V_S}}}\)

Where ω is the resonant frequency

V_{L} is the voltage across the inductor.

Vs is the supply voltage.

**Calculation:**

Given that, V_{L} = 4150 V, V_{S} = 125 V

\(S = \frac{{{V_L}}}{{{V_S}}} = \frac{{4150}}{{125}} = 33.2\)