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  1. For the circuit shown below, if the power dissipated in the 6Ω resistor is zero then V is—


    1. 20√2 ∠ 45°
    2. 20 ∠ 30°
    3. 20 ∠ 45°
    4. 20√2 ∠ 30°
Correct Option: C

The given circuit:

Given that power dissipated in the 6Ω resistor is zero, it means voltage at node 1 is same as 2 (i.e., V1 = V2)
KCL at node 1

V1 - 20    0°
+
V1
+
V1 + V2
= 0
1j16 + j8

or
V1 1 +
1
20  0°(since V1 = V2)
j1

or
V1 = 20   0°
j
.........…(i)
(j + 1)

Again KCL at node 2:
V2 – V1
+ V1 +
V2 – V
= 0
6 + j855

or
2V2
= V(since V1 = V2)
55

or
V2 =
V
...........(ii)
2

From equation (i) and (ii)
20   0°
j
=
V
j + 12

or
V =
2 × 20 0° × 90°
2 × 45°

20 2 45°
Hence alternative (A) is the correct choice.



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