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I B.Tech Semester Regular Examinations, June 2009 ELECTRICAL CIRCUITS ANALYSIS ( Common to Electrical & Electronic Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆ ⋆ ⋆ ⋆ ⋆
- (a) Find the current delivered by the source for the network shown in figure 1a using network reductions technique.
Figure 1a (b) Find the value of applied d.c. voltage for the network, shown in figure 1b. [8+8]
Figure 1b
- An iron ring of cross sectional area 800 mm^2 and of mean radius 170mm has two windings connected in series, one of 500 turns and the other of 700 turns. If the relative permeability of iron is 1200 find ,
(a) The self inductance of each coil. (b) The mutual inductance, assume that there is no leakage. Derive the formulae used. [16]
- Two coils A and B have resistance of 12Ω and 6 Ω and inductances of 0.02 and 0.03H respectively. These are connected in parallel and a voltage of 200V at 50Hz is applied to their combination. Find
(a) Current in the each coil. (b) The total current and the (c) The power factor of the circuit. (d) Power consumed by each coil and total power. [16]
- (a) Three identical impedances of (3+j4)Ω are connected in delta. Find an equiv- alent star network such that the line current is the same when connected to the same supply. (b) Three impedances of (7+j4)Ω, (3+j2)Ω and (9+j2)Ω are connected between neutral and the R, Y and B phases. The line voltage is 440V, calculate. i. The line currents and ii. The current in the neutral wire. iii. Find the power consumed in each phase and the total power drawn by the circuit. [4+12]
- (a) For the n/w shown in figure 5a, draw the oriented graph, select a tree and obtain a tie-set matrix. Write down the KVL equations from the tie-set matrix.
Figure 5a (b) For the graph shown in figure 5b, find the tie-set and cut-set matrices. [8+8]
Figure 5b
- (a) Solve for current in 5 ohms resistor by principle of super position theorem shown in figure 6a.
Figure 6a
I B.Tech Semester Regular Examinations, June 2009 ELECTRICAL CIRCUITS ANALYSIS ( Common to Electrical & Electronic Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆ ⋆ ⋆ ⋆ ⋆
- (a) A bridge network ABCD is arranged as follows: Resistance between terminals AB, BC, CD, DA and BD are 10 ohms, 30 ohms, 15 ohms, 20 ohms and 40 ohms respectively. A 4V battery is connected with negligible internal resistance is connected between terminals A and C. Determine the current through each element in the network using network reduction techniques. (b) Three equal resistances are available. Find i. Two ration of the equivalent resistances when they are connected in par- allel. ii. The ratio of the current through each elements when they are connected in parallel. [10+6]
- (a) Derive an expression for the energy stored in an inductor and a capacitor. (b) Obtain an expression for Co-efficient of coupling. [10+6]
- A series -parallel circuit consists of three branches A, B and C in parallel and branch D in series with the parallel combination. The parameters of various branches are given below: Branch A : R=2 Ω, L=0.0159H Branch B : R=0.5 Ω, C=0.00318F Branch C : R=1 Ω Branch D : R=0.4 Ω, L=2.546mH The entire circuit is connected across a voltage of 200V,50Hz. Calculate
(a) The impedance of the circuit and (b) The power consumed in each branch. [16]
- (a) Deduce the relationship between the phase and line voltages in a star con- nected circuit. (b) Three similar inductive coils, each having a resistance of 20Ω and reactance of 12.57Ω are connected in star are fed from a 3-phase, 50Hz, 200V supply. Calculate the line current and the power absorbed. [16]
- (a) Write the matrix loop equation for the given network and determine the loop currents, as shown in figure 5a and find the current through each element in the network.
Figure 5a (b) For the given graph shown in figure 5b write the tie-set schedule and obtain the relation between branch currents and link currents. [10+6]
Figure 5b
- (a) Using Norton’s theorem, find the current through the load impedance ZL as shown in figure 6a.
Figure 6a (b) State and explain reciprocity theorem. [10+6]
- (a) In the circuit shown in figure 7a, the switch S is in position 1 for a long time and brought the position 2 at time t = 0. Determine the circuit current.
Figure 7a (b) Determine the value of undamped natural frequency of oscillations of a RLC circuit with R = 10 ohms, L = 4H, C = 6F. [8+8]
I B.Tech Semester Regular Examinations, June 2009 ELECTRICAL CIRCUITS ANALYSIS ( Common to Electrical & Electronic Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆ ⋆ ⋆ ⋆ ⋆
- (a) Find the power loss in 1 ohm resistance for the network as shown in figure 1a.
Figure 1a (b) Three resistances are connected is parallel having the ration of 1:2:3 the total is 100 W when 10 V is applied to the combinations, find the values of the resitances. [10+6]
- Two long single layer solenoids have the same length and the same number of turns but are placed co-axially one with in the other. The diameter of the inner coil is 8cm and that of the outer coil is 10cm. Calculate the co-efficient of coupling. [16]
- Two coils A and B have resistance of 12Ω and 6 Ω and inductances of 0.02 and 0.03H respectively. These are connected in parallel and a voltage of 200V at 50Hz is applied to their combination. Find
(a) Current in the each coil. (b) The total current and the (c) The power factor of the circuit. (d) Power consumed by each coil and total power. [16]
- (a) Three identical impedances of (3+j4)Ω are connected in delta. Find an equiv- alent star network such that the line current is the same when connected to the same supply. (b) Three impedances of (7+j4)Ω, (3+j2)Ω and (9+j2)Ω are connected between neutral and the R, Y and B phases. The line voltage is 440V, calculate.
i. The line currents and ii. The current in the neutral wire. iii. Find the power consumed in each phase and the total power drawn by the circuit. [4+12]
- For the given network find the tie-set matrix loop currents as shown in Figure 5. Hence find the current through each element in the network. [16]
Figure 5
- (a) Solve for current in 5 ohms resistor by principle of super position theorem shown in figure 6a.
Figure 6a (b) State and explain Millmann’s theorem. [10+6]
- Derive the expression for transient response of RLC series circuit with unit step input. [16]
- Find the transformed Z - parameters of the n/w shown in figure 8: [16]
Figure 8
(b) Explain network analysis using network topology based on KVL and KCL. [8+8]
- (a) Determine the Thevenin’s equivalent across the terminals A and B as shown in figure 6a.
Figure 6a (b) Verify reciprocity theorem for the voltage V and Current I in the network shown in figure 6b. [10+6]
Figure 6b
- Derive an expression for the current response in R-L series circuit with a sinusoidal source. [16]
- For the two port n/w shown in the figure 8, the currents I 1 and I 2 entering at port 1 and 2 respectively are given by the equations. I 1 = 0.5 V 1 - 0.2 V 2 I 2 = - 0.2V 1 + V 2
Figure 8 Where V 1 and V 2 are the port voltages at port 1 and 2 respectively. Find the Y, Z, ABCD parameters for the n/w. Also find its equivalent π network. [16]
