JNTU
JNTU B.Tech II NETWORK ANALYSIS Previous Question Paper (October - 2020 - R16)
Answer any five questions. All questions carry equal marks.
Main
Clearly explain the following: i) Self inductance (L) ii) Mutual inductance (M)
Answer
i) Self Inductance (L) is the property of a coil by which it opposes any change in the current flowing through it. When current changes, the magnetic flux linked with the coil changes, inducing an electromotive force (EMF) according to Faraday's law. It is defined as the ratio of flux linkage to the current: L = NΦ / I. The unit is Henry (H).
ii) Mutual Inductance (M) is the property by which a change in current in one coil induces an EMF in a neighboring coil due to the magnetic coupling between them. It depends on the physical geometry and the magnetic coupling coefficient (k). The induced EMF in coil 2 due to current change in coil 1 is given by e₂ = -M(di₁/dt). The unit is also Henry (H).
An Iron ring of mean length 50 cms has an air gap of 1 mm and a winding of 200 turns. If the relative permeability of the Iron is 400, when a current of 1 Amp flows in the winding, determine the flux density. Neglect leakage and fringing.
Answer
Given: Mean length of iron path (l_i) = 0.5 m - 0.001 m = 0.499 m, length of air gap (l_g) = 0.001 m, turns (N) = 200, relative permeability (μ_r) = 400, current (I) = 1 A. Permeability of free space (μ_0) = 4π × 10⁻⁷ H/m.
The total magnetomotive force (MMF) is NI = 200 × 1 = 200 AT. The total reluctance (S) is the sum of iron reluctance (S_i) and air gap reluctance (S_g):
The flux (Φ) is given by MMF / (S_i + S_g). Since area (A) is common, we use the magnetic circuit equation:
Substituting the values:
The flux density is 0.1118 T.
For the network shown in below Figure find Zab and Io.
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Explain about Ideal transformer.
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Given a series RLC circuit with R = 10 Ω, L = 1 mH and C = 1 μF is connected across a sinusoidal source of 20 V with variable frequency. Find: i) The resonant frequency ii) Q factor of the circuit at resonant frequency iii) Half power frequencies.
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Derive and draw the response of a series RLC circuit for step input.
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An impedance Z1 = 10 + j10 Ω is connected in parallel with another impedance of resistance 8.5 Ω and a variable capacitance connected in series. Find C such that the circuit is in resonance at 5 KHz.
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Derive expression for R.M.S and average value of a sinusoidal alternating quantity.
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A series-connected RLC circuit has R = 4 Ω and L = 25 mH: Determine the average power dissipated at ω = ω0, ω1, ω2. Take Vm = 100 V.
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A capacitor of 100 μF is connected across 200 V, 50 Hz, Single phase supply. Calculate: i) The reactance of the capacitor ii) RMS value of the current iii) The maximum value of the current.
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When an impulse voltage is impressed across R-C circuit, derive an expression for its current response.
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Explain clearly the terms: i) Characteristic Impedance and ii) Image Transfer Constant.
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Define Hybrid parameters of a Two Port network. Establish the relation between Hybrid Parameters and ABCD Parameters.
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What is a high pass filter? In what respects it is different from a low pass filter?
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Derive the equations to find the inductances and capacitances of a constant K high pass filter.
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