# Objective Questions on Network Analysis 11

- Find i(t) when V
_{S}(t) = 100 sin(2510 t). - What is h(t) in following circuit ?
Step response is given as [1 – e
^{ -α t}]u(t). h(t) is an impulse response. - In a pure parallel LC circuit under resonance condition, current drawn from main supply is
Current in LC circuit is 0 at resonance, because of infinite of parallel LC circuit.
- Z may comprise of following circuit
Series combination of 2.5 mH and 16 μ F will result in a loss less resonant L-C circuit with constant V. But parallel combination of 2.5 mH and 16 μF will result in an exponentially increasing sinusoidal response as shown.
- In a RLC circuit (series) if C is increasing and remaining R and L are constants, then resonant frequency will be
As resonant frequency, f
_{0}, - If all the transmission zeros of a network are at infinity then it is a
So it will be a low pass filter.
- At lower half power frequency current in series R-L-C circuit has the phase relation with reference to supply voltage as
- A circuit with a resistor, inductor and capacitor in series is resonant of f
_{0}Hz. If all the component values are now doubled the new resonant frequency is - In a series RLC high Q circuit, the current peaks at a frequency
Now high Q means low R, C and high L. So bandwidth = f

_{0}/ Q. Since less bandwidth, hence sharp resonance. - A sinusoidal voltage V and frequency f connected to a series circuit at variable resistance R and a fixed reactance X. The locus of the tip of the current phase or I as R is varied from zero to infinity is
Above equation is a semicircle equation with radius V / 2X.
- In the network shown below, switch S was closed and steady state is a attained. If S is opened at t = 0 and i(t) = 2 cos 100t then what is the value of V ?
Circuit starts oscillating when switch is opened. Here I = 2, R = 2.5 Ω.
- Circuit shown below has been in steady state when switch S is opened, the current I is given by
When the switch is closed and circuit reached its steady state condition. Since inductor offers short circuit path. So I = 10 / 1 = 10 A. Now, when switch is opened,
- The current i(t) at any instant t in the network shown in the figure will be after closing the switch S at t = 0
The value of the current at t = 0
^{ + }and at t = infinity which should be zero and 10 / 1 = 10 A respectively. - A series RLC circuit consisting of R = 20 ohms X
_{L}= 20 ohms is connected across an AC supply of 200 V rms. The rms voltage across the capacitor isZ = 20 Ω. I = 200 / 20 = 10 A. V_{C}= –JIX_{C}. - In a RC circuit consisting R = 10 kΩ and phase angle between current and voltage is 45°. What is the value of C at Ω = 1 ?
So, X
_{C}/ R = 1. X_{C}= 10 kΩ. or, 1 / C = 10 kΩ. - In a series RLC circuit the phasor diagram shown as below. Which of following is true regarding phasor diagram for the series RLC circuit ?
- In a RLC series circuit consisting V
_{R}= 3 V, V_{C}= 8 V and V_{L}= 4 V, Find the value of source excitation voltage ? - In a parallel RL Circuit has i = 10 A and i
_{R}= 8 A. Find the value of current flowing through the inductor ? - If a capacitor is added in parallel with inductor C in the above question, which draws a current of 6 A then i will be
- Consider the following circuit diagram. If R = 25 Ω X
_{L}= X_{C}= 25 Ω then what is the value of θ? [ Assuming V as reference phasor. ]tanθ = X_{L}/ R.