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GATE 2016 EE (EE2) – Question 45

Electric Circuits · Transient response of DC and AC networks, sinusoidal steady-state analysis, resonance, two port networks, balanced three phase circuits, star-delta transformation, complex power and power factor in AC circuits · 2 marks · Numerical answer

The shown two-port has z11=40 Ω,z12=60 Ω,z21=80 Ω,z22=100 Ω. Find average power delivered to RL=20 Ω in watts.

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Correct answer: 34.0 to 36.0

Explanation

With port currents defined entering the two-port, V2=−20I2. The z equation gives $80I_1+100I_2=-20I_2$, so I2=−(2/3)I1.

At the input, the 20 V source and 10 Ω resistor give $20=10I_1+V_1=50I_1+60I_2$. Substitution gives I1=2 A and I2=−4/3 A.

The load power is $I_2^2R_L=(16/9)20=$ **35.5556 W**, within 34–36 W.

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