ECE

NETWORK THEORY PART -6

76.What is transfer point impedance?

It is defined as the ratio of voltage transform at one port to the current transform at the other port.

77. Define resonant circuit.

The circuit that treat a narrow range of frequencies very differently than all other frequencies.These are referred to as resonant circuit.The gain of a highly resonant circuit attains a sharp maximum or minimum as its resonant frequency.

78. When the circuit is said to be in resonance?

1.A network is in resonance when the voltage and current at the network input terminals are in phase.

2.If inductive reactance of a network equals capacitive reactance then the network is said to be
resonance

79.What is resonant frequency ?

The frequency at which resonance occurs is called resonance frequency.

                                                          


80. Define bandwidth.

The bandwidth (BW) is defined as the frequency difference between upper cut-off frequency (f2) and
lower cut-off frequency (f1)
Bandwidth = f2-f1
Where f2 upper cut-off frequency
F lower cut-off frequency

81. Define half power frequencies ?

The frequencies at which the power is half the maximum power are called half power frequencies          
                                     



82.What is the formula to find the power factor in a three phase circuits.

Tan Ø= 3(W2-W1)/(W1+W2)

83. What is the formula to find the reactive power in three phase circuits.

3(W2-W1)= 3ELILsin Ø

84. What is the formula to find the power in a three phase circuits.

Power= 3ELILCos Ø

85.What is the advantage of using three phase rather than using three single phase circuits.

Three phase system have uniform torque and self starting.

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