ECE

NETWORK THEORY PART-4

45. What is instantaneous power?

The power at any instant of time is known as instantaneous power.
P (t) = v(t) . I (t)

46. What is average power?

The average of the instantaneous power over one period is called average power. Average power is also defined as the product of voltage and current.

47. What is apparent power?

The product of Vrms and Irms is known as the apparent power (s).
Apparent power (S) = V Eff I Eff VA

48. Define power factor.

The ratio of the average power to the apparent power is called the power factor.


      Power Factor =            Average power       
                                          Apparent Power

49. What is power triangle ?

A commonly employed graphical representation of complex power is known as the power triangle.

50. Define complex power

The product of the rms voltage phasor and the complex conjugate of the rms current phasor is known as complex power. It is denoted as S and it is measured in volt-amperes (VA)
The complex power is S = ½ V i*


51.What is reactive power?

It is defined as product of the applied voltage and the reactive component of the current. It is
also called as imaginary component of the apparent power.It is represented by “Q” and it is measured in unit volt- ampere reactive (VAR).
Q = VEff IEff sin VAR

52What is the equation for determining the number of independent loops in mesh current method?
 
L = b-n +1
Where,
L = number of loops
B= number of branches
N= number of nodes.

52.On which law is the mesh analysis based?
Mesh analysis is based on Kirchoff’s voltage law.

53. On which law is the nodal analysis based?
Nodal analysis is based on Kirchoff’s current law and Ohm’s law.

54. What is mesh analysis?

Mesh analysis is one of the basic techniques used for finding current flowing through the loop in a network. Mesh analysis is applicable if the given network contains voltage sources.If therer exist current sources in a circuit, then it should be converted into equivalent voltage sources.

55. What is nodal analysis?

Nodal analysis is one of the basic techniques used to finding solution for voltage drop
across the nodes in a given circuit. Nodal analysis is applicable if the given network contains current sources.If there exists voltage sources in the given circuit, then it can to be converted into equivalent current sources.

56. When do we go for supermesh analysis.

If the branches in the network has a current source, then it is slightly difficult to apply mesh analysis.One way to over come this difficulty is by applying the supermesh technique.
In this case we have to choose supermesh. A supermesh is constituted by two adjacent loops that have common current source.

57. When do we, go for supernode analysis.

If the branches in the network has a voltage source, then it is slightly difficult to apply nodal
analysis. One way to overcome this difficulty is by applying the supernode technique.
In this case, we have to choose super node. A supernode is constituted by two adjacent node that have common voltage source.

58. State superposition theorem.

Any electric circuit (linear, lumped, bilateral), is energeied by two or more sources,the
response in any element in the network is equal to the algebraic sum of the responses caused
byindividual sources acting separately.

59. State Thevenin’s Theorem.

A complex network having linear, bilateral, lumped elements with open circuited output
terminals can be reduced by a simple circuit consisting of a single voltage source in series with a impedance.

60. State Norton’s theorem.

Any electrical network (linear, lumped, bilateral) with short circuited terminals can be
reduced by a simple circuit consisting of a single current source in parallel with a Thevenin’s
equivalent resistance.

61. State Maximum power transfer theorem.

Power transferred from source to load will be maximum, when source resistance is equal to load resistance looking back from its load terminals.

62. Define duality.

Two electrical network which are governed by the same type of equations are called duality.

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