APPLIED PHYSICS OEL REPORT
GROUP MEMBERS
MUHAMMAD HASSAAN (TC-24029)
ZAIN-UL-ABEDEEN (TC-24024)
ABDUL AZZAQ (TC-24032)
SYED SUMAIL (TC-24031)
MUHAMMAD AHMED (TC-24023)
OBJECT: TO STUDY THE CHARACTERISTICS OF REJECTOR SCIRCUIT AND DETERMINE
UNKNOWN CAPACITANCE.
APPARATUS: Resistance, Inductor, Capacitors, a frequency generator/oscillator, Oscilloscope,
Connecting wires, A.C supply etc.
THEORY: Rejector circuit also known as “RLC-Parallel”, “Parallel Resonance Circuit”, “Parallel
tuned circuit” is a circuit in which an inductor L and capacitor C are connected in parallel to each
other (whereas resistors in series) with a source emf E.
The total opposition offered by RLC circuit is known as Impedance Z. It depends on frequency of AC
signal applied and given by: -
Where Xl = wL and Xc=1/wC are inductive and capacitive reactance of inductor ad capacitor
respectively.
We see that at resonance frequency inductive reactance cancels capacitive reactance therefore
impedance is infinite so the current almost reduces to zero.
I0 = Eo/z
WORKING FORMULA:
Inductance in given by: -
L = 1/4π2f2c
PROCEDURE:
1. The first step is to make connections as i.e: take a resistor, an inductor and a capacitor of
suitable and connect them in parallel and connect frequency generator and cathode ray
oscillator.
2. Apply a signal of certain voltage by the oscillator at a certain frequency and note down the
amplitude of output signal from CRO.
3. Now start increasing frequency of input signal (Keeping the voltage constant) step by step,
each time note down the amplitude of the output signal decreases as frequency increases
and reaches a minimum value then start increasing again.
4. Plot a graph between frequency (f) on x-axis and the corresponding amplitude of the signal
on y-axis for each set of observation on one graph paper.
5. From graph calculate resonant frequencies for capacitor at which amplitude of signal is
minimum.
6. Calculate the inductance with the help of resonant frequencies obtained from graph.
FROM GRAPH:
Resonant frequency (f) = __________ KHz
L = 1 / 4π2f2C => C = 1 / 4π2f2L
RESULT:
1. Characteristics of rejector circuit studied. It is seen that at resonant frequency the output
signal is minimum.
2. The value of capacitance is: - I _______ mH.
CIRCUIT DIAGRAM:
PICTURES DURING OEL PERFORMANCE:
