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Q7.11 (b)  Figure shows a series LCR circuit connected to a variable frequency 230\: V source. Obtain the impedance of the circuit and the amplitude of current at the resonating frequency. (\text{where,}\ L=5H, C=80\mu F \ \text{and} R=40\Omega)  

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Given: Variable frequency supply voltage V=230V

Inductance L=5.0H

Capacitance C=80\mu F=80*10^{-6}F

Resistance R=40\Omega

Now, The impedance of the circuit is 

Z=\sqrt{(wL-\frac{1}{wC})^2+R^2}

At Resonance Condition:

 wL=\frac{1}{wC}

Z=R=40\Omega

Hence, the Impedance at resonance is 40\Omega.

Now, at resonance condition, impedance is minimum which means the current is maximum which will happen when we have a peak voltage, so

Current in the Resonance circuit is Given by,

I_{resonance}=\frac{V_{peak}}{Z}=\frac{\sqrt{2}* 230}{40}=8.13A

Hence, the amplitude of the current at resonance is 8.13 A.

 

Posted by

Pankaj Sanodiya

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