#### Question: Define the term ‘Resonance’ as applicable to simple RLC series circuit. Discuss briefly effect of Resonance on circuit performance. OR Explain resonance condition RLC parallel circuit.

**Series resonance**

A series circuit is said to be at electrical resonance when its net reactance is zero.The frequency (F_{r}) at which resonance occurs is called **Resonant frequency** ( F_{r}).

**Resonance conditions for series circuit**

- Impedance of resonance is only resistance i.e Z=R

- Net reactance is zero

therefore, X =X_{L} – X_{c } = 0

X_{L = }X_{c}

- V
_{L }-V_{c }= 0

V_{L }= V_{c}

- Maximum current i.e line current, Imax = V/R
- Phase angle at resonance is zero.
- Therefore,power factor is unity (cos 0 = 1 )
- X
_{L }=X_{C}

**Resonance frequency **

f_{r} =

**Quality factor (Q factor)**:

**The resonance condition in RLC Parallel circuit**

# Q: Current in AC series R-L-C circuit at resonance

The net reactance in R-L-C circuit shown in figure is,

If for same frequency of the applied voltage X_{L} = X_{C} (in magnitude) then X = 0 and Z = R as shown in figure (c). From figure (c), V_{L} = IX_{L} and V_{C} = IX_{C} and these two are equal in magnitude but opposite in phase.Hence, they cancel each other. The applied voltage, V drops entirely across R. So that V = V_{R}. The circuit impedance Z = R. The phasor diagram for series resonance is shown in figure (d). It means that impedance of the circuit equals the ohmic resistance R, so that current is maximum in AC series R- L-C circuit.

## A.C. CIRCUITS TOPIC

- Introduction Of AC Circuits In Electrical Engineering
- How emf is induced in single phase system ? single phase generation .
- Explain what is ac quantity : and Advantages of AC over DC in circuits
- What is waveform, amplitude, cycle, time-period, phase & phase difference
- Define RMS & average value as applied to A.C. voltage & current
- What is form factor? crest factor? peak factor? & power factor? in ac circuits
- what is phasor diagram, phasor algebra, leading & lagging ac quantities
- Phasor representation of alternating quantities – resistive, inductive, capacitive
- What is R-L-C series connection for A.C. circuit ? Explanation
- What is series combination of R-L circuit ? Explanation
- Define what is active power, reactive power, apparent power & power factor
- Explain what is series combination of R-C circuit in electrical engineering
- What is simple parallel AC circuits ? Explanation -electrical engineering
- Resonance as applicable to simple RLC series circuit? effect on circuit performance
- Explain three phase generation of voltage ? electrical engineering
- Explain in detail about what is star and delta three phase system ?
- Relation between phase voltage & line voltage in case of balanced star connected load
- relationship between line current & phase current for delta connected 3 load
- Relation between power consumed in a balanced star & delta connection

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