# Electrical Engineering - RLC Circuits and Resonance - Discussion

### Discussion :: RLC Circuits and Resonance - General Questions (Q.No.1)

1.

A 10 resistor, a 90 mH coil, and a 0.015 F capacitor are in series across an ac source. The impedance magnitude at 1,200 Hz below fr is

 [A]. 1,616 [B]. 161 [C]. 3,387 [D]. 1,771 Explanation:

No answer description available for this question.

 Bharamu said: (Jul 27, 2011) fr = 1/ 2*Pi*sqrt(L*C)

 Rao said: (Oct 25, 2011) XL=2*Pi*F*L Z=Sqrt of(R^2+(XL-XC)^2)

 Dinesh said: (Feb 27, 2012) fr = 1/ 2*Pi*sqrt(L*C) (or) XL=2*Pi*F*L Z=Sqrt of(R^2+(XL-XC)^2)

 Kananya said: (Mar 9, 2012) We know that formula for Impedence(Z) Z=Sqr root of (R^2+(Xl-Xc)^2) Here R=Resistance Xl=wl (w=2*3.14*f) and l=inductance of a coil Xc=1/wc Here c=capacitance of capaciter Z=Sqr root of (R^2+(Xl-Xc)^2)

 Teju said: (Dec 12, 2012) XL=WL=(2*PI*f)L XC=1/WC=1/(2*PI*f)C where,L=90mh,C=.015microF, f=1200hz and R=10ohm Z=sqrt of(R^2+(XL-XC)^2)

 Rahul Mishra said: (Aug 20, 2013) IN RLC SERIES CIRCUITS WE KNOW: Z = (jw)^2+(jw)R/L+1/LC.

 Mrakovic said: (Nov 12, 2013) fr = 1/2*pi*sqrt of LC. fr = 4331.648. f = fr-1200Hz=3131.64. Z = sqrt of(R^2+(XL-XC)^2). Z = 1617 ohm.

 Babu said: (Dec 26, 2013) We know that, Resonance frequency: Fr = 1/2*pi*sqrt(L*C). Xl = Wl = 2*3.14*f*l. Xc = 1/wc.

 Durai said: (Feb 24, 2014) fr = 1/2*pi*sqrt (L*c).

 Manindra said: (May 19, 2014) Fr = 1/2*pi*sqrt(L*c)=4331.648. f = fr-1200Hz = 3131.64. Xl = Wl = 2*3.14*3131.64*l. Xc = 1/wc. Z = sqrt of(R^2+(XL-XC)^2) = 1616 ohm.

 Aggrey Kere said: (Jun 26, 2014) From R-L-C circuit above, we know that; Z=root of R^2+(XL-XC)^2. but XL=2pi*fr*L. XC=1/2Pi*fr*C.

 Robert said: (Oct 1, 2014) XL=2*3.14*F*L THIS IS THE FORMAL. I WAS ASK TO MAKE SO I CAN FIND UNKNOWN F AND L. MOVE THING AROUND I CAME UP WITH SO ARE THESE RIGHT. F=2*PI*L*XL. L=2*PI*F*XL.

 Prashant said: (Jan 20, 2015) I think result is not coming from above all formula I want real answer from you friends please reply.

 Shwetha said: (Jun 11, 2015) Its (xl-xc). Because xl is greater than xc.

 Rajat Dey said: (Jun 25, 2015) I know above formula but this is very long process and heavy time span. So how can do it quickly? Please help me.

 Shailu said: (Aug 7, 2015) Is it correct? Above explained examples?

 Dinesh said: (Dec 4, 2016) Quicker method needed.

 Puja said: (Jan 15, 2017) Yes, I agree @Prashant.

 Siddu Bhandarkavathe said: (Aug 29, 2017) It is 1/2 π √ LC.

 Hassan said: (Jun 26, 2018) How we can change the units?

 Sushma said: (Jul 4, 2019) 1/z = √ [(1/R)^2+(1/Xl-1/Xc)^2] for RLC circuit.