At resonance 𝑋𝐿 = 𝑋𝐶 , 𝐿𝑚𝑖𝑛 =R
Different graphs
i - graph
Because Z is minimum
When frequency is lover Conclusion → When
then resonating frequency is higher and ckt
At lover frequency At higher frequency
frequency current leads capacitive reactance inductive reactance is
is R-L-C, voltage must lead
voltage because ckt is in high so when high 𝑋𝐿 = 𝜔𝐿 so when current be because ckt is
frequency is less frequency is must then
capacitive in nature then resoning resonatingh frequency. inductive in nature
frequency ckt must Ckt must be inductive in
be capacitive nature.
Resonating
frequency
Different graphs
z - graph
Different graphs
Y - graph
Different graphs
(XL , XC) - graph
Different graphs
X - graph
Half power frequencies and band width
Quality factor (Q - factor) of series resonant circuit
In the circuit shown below, what will be the readings of the voltmeter and
ammeter
(a) 800 V, 2A
(b) 300 V, 2A
(c) 220 V, 2.2 A
(d) 100 V, 2A
In the circuit shown in fig. neglecting source resistance the voltmeter and
ammeter reading will respectively will be
(a) 0V, 3A
(b) 150 V, 3A
(c) 150 V, 6A
(d) 0V, 8A
Which of the following plots may represent the reactance of a series LC
combination
(a) a
(b) b
(c) c
(d) d
The voltage across a pure inductor is represented by the following
diagram. Which one of the following diagrams will represent the current
A circuit drawn a power of 550 watt from a source of 220 volt, 50 Hz. The
power factor of the circuit is 0.8 and the current lags in phase behind the
potential difference. To make the power factor of circuit as 1.0 , the
capacitance required to be connected with it, will be
(a) 70.4 𝜇𝐹
(b) 75 𝜇𝐹
(c) 7.5 𝜇𝐹
(d) 750 𝜇𝐹
In the circuit given below. What will be reading of the voltmeter
(a) 300 V
(b) 900 V
(c) 200 V
(d) 400 V
In pure inductive circuit, the curves between frequency f and reciprocal of
inductive reactance 1/XL is
In the circuit shown here a 30 V dc source gives a current 2.0 A, and a 30 V
ac source of frequency 100 Hz gives a current 1.2 A. The inductive
reactance is
(a) 10 ohm
(b) 20 ohm
(c) 5 34 𝑜ℎ𝑚
(d) 40 𝑜ℎ𝑚
A resistor R, an inductor L, a capacitor C and voltmeters V1, V2 and V3 are
connected to an oscillator in the circuit as shown in the adjoining diagram.
When the frequency of the oscillator is increased, then at resonant
frequency the reading of voltmeter V3 is equal to
(a) That of voltmeter V1
(b) That of voltmeter V2
(c) Both of the voltmeters V1 and V2
(d) None of these
An ideal choke takes a current of 10 amp when connected to an ac supply
of 125 volt and 50 Hz. A pure resistor under the same conditions takes a
current of 12.5 amp. If the two are connected to an ac supply of 100 2
volt and 40 hertz, then the current in a series combination of the above
resistor and inductor is
(a) 1 amp
(b) 12.5 amp
(c) 20 amp
(d) 25 amp
A bulb and a capacitor are connected in series to a source of alternating
current. If its frequency is increased, while keeping the voltage of the
source constant, then
(a) Bulb will give more intense light
(b) Bulb will give less intense light
(c) Bulb will give light of same intensity as before
(d) Bulb will stop radiating light
The band width of a series resonant circuit is 500 Hz and the resonant
frequency is 5000 Hz. The quality factor of the circuit will be
(a) 40
(b) 20
(c) 10
(d) 5
In the LCR series circuit the voltmeter and ammeter reading are
(a) V = 100 volt, i = 2 amp
(b) V = 100 volt, i = 5 amp
(c) V = 300 volt, i = 2 amp
(d) V = 300 V, i = 1 amp
Following figure shows an ac generator connected to a "block box"
through a pair of terminals. The box contains possible R, L, C or their
combination, whose elements and arrangements are not known to us.
Measurements outside the box reveals that
e = 75 sin (sin t) volt, i = 1.5 sin ( t + 45o) amp
then, the wrong statement is
(a) There must be a capacitor in the box
(b) There must be an inductor in the box
(c) There must be a resistance in the box
(d) The power factor is 0.707
An alternating e.m.f. of angular frequency 𝜔 is applied across an
inductance. The instantaneous power developed in the circuit has an
angular frequency
𝜔
(a)
4
𝜔
(b)
2
(c) 𝜔
(d) 2𝜔
10−4
The ac current through a capacitor 𝐶 = farad is given by
314
𝑖 = 25 cos 314𝑡 + 30° 𝑚𝐴 then the e.m.f. across the capacitor will be
given by
(a) e = 250 cos (314 t – 60o) volt
(b) e = 250 sin (314 t –+30o) volt
(c) Both of the above
(d) None of these
An LCR circuit contains 𝑅 = 50Ω, L = 1mH and 𝐶 = 0.1𝜇𝐹 . The
impedance of the circuit will be minimum for a frequency of
105 −1
(a) 𝑠
2𝜋
106 −1
(b) 𝑠
2𝜋
(c) 2𝜋 × 105 𝑠 −1
(d) 2𝜋 × 106 𝑠 −1
An alternating current source of frequency 100 Hz is joined is a
combination of a resistance, a capacitance and a coil in series. The
potential difference across the coil, the resistance and the capacitor is 46,
8 and 40 volt respectively. The electromotive force of alternating current
source in volt is
(a) 94
(b) 14
(c) 10
(d) 76
