Network Elements and the Concept of Circuit

Network Elements and the Concept of Circuit

Easy Questions

Network Theory

Network Elements and the Concept of Circuit
Network theory miscellaneous

Direction: A coil of inductance 10 H and resistance 40 Ω is connected as shown in the figure. After the switch S has been in contact with point 1 for a very long time, it is moved to poin 2 at t = 0.

  1. If, at t = 0+, the voltage across the coil is 120V, the value of resistance R is—










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    t < 0 connect to 1

    i L(0–) =
    120
    		 = 2 Amp
    20 + 40

    i L(0–) = i L(0+) = 2 Amp
    t = 0+ connect 2
    (60 + R) 2 – 120 = 0
    60 + R = 60
    or R = 0Ω
    Hence alternative (A) is the correct choice.


    Correct Option: A

    t < 0 connect to 1

    i L(0–) =
    120
    		 = 2 Amp
    20 + 40

    i L(0–) = i L(0+) = 2 Amp
    t = 0+ connect 2
    (60 + R) 2 – 120 = 0
    60 + R = 60
    or R = 0Ω
    Hence alternative (A) is the correct choice.


  1. A series R-L-C circuit is switched on to a step voltage V at t = 0. What are the initial and final values of the current in the circuit, respectively?








  1. View Hint View Answer Discuss in Forum

    Zero, zero
    because at initial capacitor short 4 inductor open and at final capacitor open 4 inductor short.

    Correct Option: C

    Zero, zero
    because at initial capacitor short 4 inductor open and at final capacitor open 4 inductor short.

  1. In figure, the capacitor initially has a charge of 10 coulomb. The current in the circuit one second after the switch S is closed will be—










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    I(+) =
    V
    		 e–t/RC
    R

    =
    100
    		 e–1 / 2 × .5
    R

    = 18·5 A

    Correct Option: B

    I(+) =
    V
    		 e–t/RC
    R

    =
    100
    		 e–1 / 2 × .5
    R

    = 18·5 A

  1. The circuit shown in the figure is in steady state, when the switch is closed at t = 0. Assuming that the inductance is ideal, the current through the inductor at t = 0+ equals—










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    At steady state iL(0–) =
    10
    		 = 1Amp
    10

    i L(0–) = i L(0+) = 1 Amp

    Correct Option: C

    At steady state iL(0–) =
    10
    		 = 1Amp
    10

    i L(0–) = i L(0+) = 1 Amp

  1. In the figure given, for the initial capacitor voltage is zero. The switch is closed at t = 0. The final steady-state voltage across the capacitor is—










  1. View Hint View Answer Discuss in Forum

    Capacitor will fully charge act an open.

    I =
    20
    		 = 1Amp
    10 + 10

    VC(0–) = 0 (given)
    VC(∞) = Voltage across 10Ω terminal VC(∞) = 10 × 1
    = 10V


    Correct Option: A

    Capacitor will fully charge act an open.

    I =
    20
    		 = 1Amp
    10 + 10

    VC(0–) = 0 (given)
    VC(∞) = Voltage across 10Ω terminal VC(∞) = 10 × 1
    = 10V