Download 4. RLC series resonance

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EXPERIMENT NO. 4
AIM: Study the Phenomenon of Resonance in RLC series circuit & obtain the Resonance
Frequency.
APPRATUS REQUIRED:
Sl. No.
1.
2.
3.
4.
5.
6.
7.
Equipments
Single Phase AC Supply
Variable Frequency Signal
Generator
AC Ammeter
Inductor
Capacitor
Resistor
Connecting Wires
Type
AC
AC
MI
Specification
230 volts, 50 Hz
1 HZ –Mhz, (0-10)Volts,
Sine Wave
(0-10) mA
10, 20, 30 mH
10, 20, 30 nF
100 ohm
PVC Insulated
Quantity
1 no.
1 no.
1 no.
1 no.
1 no.
1 no.
As per ckt.
requirement
THEORY:
In a circuit, consisting of reactive components of opposite nature i.e., L & C, if we change the
variables F, L or C there comes a situation when over all impedance(or Admittance) of the circuit
becomes purely resistive (or conductive G). Such a condition is called “RESONANCE”.
In Resonance condition, Output becomes much larger than the excitation.
Let us consider the circuit shown in fig. (1)
Applying the KVL we get:
Where;
& the magnitude of current
Now, at Resonance, we have:
Since,
2
Now, Z=R,
as (XL=XC)
Therefore,
Variations of current with respect to frequency are shown in the Graph. When current is
maximum, the ckt is said to be in resonance. So, in resonance condition Z should be minimum.
Thus, in this condition current is in phase with voltage, Power Factor Becomes unity &
impedance Z=R;
CIRCUIT DIAGRAM
Figure(1): Circuit Diagram for RLC Series Resonance
Figure(2): Series Resonance curve
PROCEDURE:
1. Make the connections as per the circuit diagram.
2. Switch on the supply keeping source frequency of the signal generator at lowest.
3. Take the value of frequency & current as per the observation table.
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4. Increase the value of Frequency & take the reading still it current reaches its maximum
value.
5. If the frequency is increased further, the current start decreasing again, take few more
readings upto maximum frequency range of the available source.
6. Take at least 10-12 readings to cover the complete range, of variations of current
around maximum value.
7. Now draw a graph between, Current & Frequency.
OBSERVATION TABLE:
Sl. No.
Reading of
Signal Generator
Frequency in
(KHz)
Ammeter
Reading I(mA)
Frequency
corresponding to
maximum Current
CALCULATIONS:
1. Resonance Frequency:
Hz
2. Percentage Error in Resonance Frequency
OBSERVATIONS:
Value Given: R=_____________ohm,
L=___________mH, C=_____________nF
Applied Voltage=___________ Volts, Frequency=__________Hz (calculated)