Network theory miscellaneous


  1. For the circuit shown below, the current supplied by the sinusoidal current source I is—











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    The given circuit:

    The current supplied sinusoidal current source
    I = IR2 + IL2
    or
    I = 122 + 162 = 144 + 256
    = 400 = 20A.

    Correct Option: C

    The given circuit:

    The current supplied sinusoidal current source
    I = IR2 + IL2
    or
    I = 122 + 162 = 144 + 256
    = 400 = 20A.


Direction: Statement for Q. 103 to Q. 105. A signal generator supplies a sine wave of 20V, 5kHz to the circuit shown below—

  1. The phase angle of the circuit—









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    Phase angle,

    φ = tan–1
    XC
    R

    or
    φ = tan–1
    0·126
    = 33°
    0·2

    Correct Option: A

    Phase angle,

    φ = tan–1
    XC
    R

    or
    φ = tan–1
    0·126
    = 33°
    0·2



  1. The total impedance of the circuit—









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    Total impedance of the circuit,

    ZT =
    Vs
    =
    20     0°
    IT0·24 × 33°

    = 83.3 -33°Ω

    Correct Option: B

    Total impedance of the circuit,

    ZT =
    Vs
    =
    20     0°
    IT0·24 × 33°

    = 83.3 -33°Ω


  1. The phase angle for the circuit shown below is—











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    The given circuit:

    From above circuit,
    XL = 2πf L = 2 × 3·14 × 100 × 70 × 10–3
    = 43·98Ω
    Now,
    Zeq = (40 + j43·98)Ω
    Current,

    I =
    Vs
    =
    30 0°
    Zeq40 + j43·98

    ≈ 0·5 – 47·7°A
    Thus, we conclude that current lags behind the applied voltage by 47·7°. Hence the phase angle between voltage and current, θ = 47·7°.

    Correct Option: A

    The given circuit:

    From above circuit,
    XL = 2πf L = 2 × 3·14 × 100 × 70 × 10–3
    = 43·98Ω
    Now,
    Zeq = (40 + j43·98)Ω
    Current,

    I =
    Vs
    =
    30 0°
    Zeq40 + j43·98

    ≈ 0·5 – 47·7°A
    Thus, we conclude that current lags behind the applied voltage by 47·7°. Hence the phase angle between voltage and current, θ = 47·7°.



  1. The given circuit is a combination of—











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    The given circuit:

    The impedance of the given circuit

    Z =
    30 + j50
    =
    30   0°
    =
    58·31   59°
    I– 5 + j1515·81 – 108·43°

    = 3·69 – 49·43° or Z = (2·4 – j 2·8)Ω
    Therefore, the circuit has a resistance of 2·4Ω in series with capacitive reactance 2·8Ω.

    Correct Option: A

    The given circuit:

    The impedance of the given circuit

    Z =
    30 + j50
    =
    30   0°
    =
    58·31   59°
    I– 5 + j1515·81 – 108·43°

    = 3·69 – 49·43° or Z = (2·4 – j 2·8)Ω
    Therefore, the circuit has a resistance of 2·4Ω in series with capacitive reactance 2·8Ω.