Electrical Circuit & Network

Sub code: 318(S)

Unit-1 1. Short Question(Each carry one marks):

i. Define with example: active element, passive element, unilateral element, bilateral element, linear circuit, non-linear circuit, lump network, distributed network.

ii. What is the formula of energy stored in inductor? iii. What is the formula of energy stored in capacitor? iv. What is voltage source? v. What is current source? vi. What is dependent source? vii. What is independent source? viii. What is ideal voltage source? ix. What is ideal current source? x. What is the formula of RMS value? xi. What is the formula of Average value? xii. What is form factor? xiii. What is peak factor? xiv. What is the phase angle between V and I in case of pure resistive circuit? xv. What is the phase angle between V and I in case of pure inductive circuit? xvi. What is the phase angle between V and I in case of pure capacitive circuit?

2. (a) Define the terms R.M.S value and Average value of an alternating quantity. (b) Briefly describe about the classification of energy source used in electrical circuit. (c) What do you mean by practical voltage source and practical current source?

Explain the concept of source transformation. 3+3+4=10

Unit-2 3. Short Question(Each carry one marks):

i. What is reactance? ii. What is inductive reactance? iii. What is capacitive reactance? iv. What is impedance? v. What is the formula of complex impedance? vi. What is the phase angle between V and I in case of R-L series circuit? vii. What is the phase angle between V and I in case of R-C series circuit? viii. What is impedance triangle? ix. What is power factor?

x. What is the example of unity power factor? xi. What is the example of lagging power factor? xii. What is the example of leading power factor? xiii. What is example of zero power factor? xiv. What is power triangle? xv. What is the formula of active power in case of three phase circuit? xvi. What is the formula of reactive power in case of three phase circuit? xvii. What is the formula of apparent power in case of three phase circuit? xviii. What are the units of active, reactive and apparent power? xix. What is the formula of complex power? xx. What Q-factor? xxi. What is selectivity or sharpness of resonance? xxii. What is bandwidth? xxiii. What is half power frequency? xxiv. Why Q-factor of series resonance circuit is called voltage magnification factor? xxv. Why Q-factor of parallel resonance circuit is called current magnification

factor? xxvi. What is rejecter circuit? xxvii. What is accepter circuit?

4. (a) Write the properties of series resonance circuit. (b) Write the properties of parallel resonance circuit. (c) Compare between series and parallel resonance circuit. 3+3+4=10

5. (a) In a RL series circuit, impressed voltage is v(t)=5sin(314t+200)V and the resulting current is i(t)=0.5sin(314t-100)A. Obtain the value of R and L. (b) The current in a circuit is given by (4.5+j12), when the applied voltage is

(100+j150). Determine (a) the complex expression for the impedance whether it is inductive or capacitive, (b) the power and (c) the phase angle between the current and voltage. 5+5=10

6. (a) Explain the phenomenon of resonance in series and parallel circuit. What is the quality factor? (b) A series RLC circuit consist of resistor R an inductance of 0.245H and a capacitor of

unknown value. When this circuit is energized by 230<00, 50Hz supply, the current is 2.3<00Amp. Calculate i. The value of capacitor ii. The voltage across inductor iii. Total power consumed at resonance. 5+5=10

Unit -3

7. State and explain KVL and KCL law. 2+2=4 8. (a) Find the current flowing through 1ohm resistance by mesh analysis in fig. below.

(b) Find the magnitude and direction of current through AB branch by nodal analysis in fig. below.

5+5=10

Unit-4

9. (a) State and explain Thevenin’s Theorem. What are the applications and limitation of this theorem? (b) State and explain maximum power transfer theorem. 3+4+3=10

10. (a) State and explain Superposition theorem.

(b) Find the current through 10 ohm resistance by Thevenin’s theorem in fig. below.

4+6=10

11. (a) State and explain Norton’s theorem

(b) Find the value of R in fig. such that the maximum power transfer occur. What is

the amount of this power?

4+6=10

Unit-5

12. Short questions:

i. What is time constant of R-L circuit?

ii. What is the time constant of R-C circuit?

(a) Derive the expression of current of R-C circuit excited by d.c. source and show that

initially capacitor acts as short circuit. 1+1+5+3=10

13. (a) Derive the expression of current of R-L circuit excited by d.c. source and show that

the voltage across resistor is exponentially rise and voltage across inductor is

exponentially decaying.

(b) A d.c. voltage of 100 volt is applied to a coil having R= 10Ω, L=10H. What is the

value of the current 0.1 sec later the switch on? What is the time taken by the

current to reach half of its final value? 5+5=10

14. (a) A resistance R and 5µF capacitor are connected in series across a 100 volt d.c.

supply, calculate the value of R such that voltage across the capacitor becomes 50 volt

in 5 sec after the circuit is switched on.

(b) A RC series circuit having R=10Ω and C=5µFis excited by 25V dc supply. Obtain the

expression of current i(t) in the time domain. 5+5=10

Unit- 6

15. (a) Define the Laplace transform. Proof the initial value theorem in the context of

Laplace transform.

(b) Obtain the Laplace transform of unit impulse function

(c) Write few properties of Laplace Transform.

(d) Obtain the Laplace Transform of unit step function

(e) Obtain the Laplace Transform of ramp function

(f) Obtain the Laplace Transform of exponential function

(g) Obtain the Laplace Transform of sinwt

(h) Obtain the Laplace Transform of coswt

(i) Obtain the Laplace Transform of f(t) = (1- e-at)

(j) Obtain the Laplace Transform of f(t) = t2

(k) Obtain the Laplace Transform of f(t) = eat.t

(l) Proof the final value theorem in the context of Laplace transform.

(m) Obtain the current expression of R-L series circuit in time domain when excited by

dc supply.

(n) Obtain the current expression of R-C series circuit in time domain when excited by

dc supply.