Electrical Engineering ⇒ Topic : Resonance Curve
The curve between current and frequency is known as resonance curve. Fig. (a) shows the resonance curve of a typical R-L-C series circuit. Note that current reaches its maximum value at the resonant frequency (fr), falling off rapidly on either side at that point. It is because if the frequency is below fr, Xc> XL and the net reactance is no longer zero. If the frequency is above fr, then XL> Xc and the net reactance is again not zero. In both cases, the circuit impedance will be more than the impedance Zr(=R) at resonance. The result is that the magnitude of circuit current decreases rapidly as the frequency changes from the resonant frequency. Note also the effect of resistance in the circuit. The smaller the resistance, the greater the current at resonance and sharper the curve. On the other hand, the greater the resistance, the lower the resonant peak and flatter the curve See Fig. (a).
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