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Alternating Cur...

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  • Question 1
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    Two coils AA and BB are connected in series across a 240 V,50 Hz240\ \text{V}, 50\ \text{Hz} supply. The resistance of AA is 5 Ω5\ \Omega and the inductance of BB is 0.02 H0.02\ \text{H}. The power consumed is 3 kW3\ \text{kW} and the power factor is 0.750.75. The impedence of the circuit is

  • Question 2
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    In a circuit inductance LL and capacitance CC are connected as shown in figure. A1{A}_{1} and A2{A}_{2} are ammeters.
    When key KK is pressed to complete the circuit, then just after closing key (K)(K), the readings of A1{A}_{1} and A2{A}_{2} will be

  • Question 3
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    Directions For Questions

    When you join your new assignment, on the very first day your boss gives you an inductor and asks you to find its inductance. You are provided an AC voltmeter of high impedance, a resistor, a capacitor and an AC source of variable frequency. You recall from your physics class that if R, L and C are connected in series current is maximum at resonance. Since you are not provided an ammeter yon drop this idea. To measure inductance, however, on the advice of an experienced colleague you connect L, R and C in series with the AC source of variable frequency.

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    You apply f=12πLC\displaystyle f = \frac{1}{2\pi \sqrt{LC}} to find L. Which frequency will you select?

  • Question 4
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    In the circuit shown in fig., the resonant frequency is

  • Question 5
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    If resistance of 100Ω100\Omega and the inductance of 0.50.5 henry and capacitance of 10×10610\times {10}^{6} farad are connected  in series through 5050Hz A.C supp;y, then impedence is

  • Question 6
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    An alternating voltage of 220V,50Hz220V,50Hz frequency is applied across a capacitor of capacitance 2μF2\mu F. The impedence of the circuit is:

  • Question 7
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    In the given circuit, the current drawn from the source is

  • Question 8
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    Directions For Questions

    Under certain conditions voltages as small as 10 V can be dangerous, and should not be regarded with anything but respect and caution.
    On the positive side, rapidly alternating currents can have beneficial effects. Alternating currents with frequencies of the order of 106Hz10^6 Hz do not interfere appreciably with nerve processes, and can be used for therapeutic heating for arthritic conditions, sinusitis, and a variety of other disorders. If one electrode is made very small, the resulting concentrated heating can be used for local destruction of tissue, such as tumors, or even for cutting tissue in certain surgical procedures.
    Study of particular nerve impulses is also an important diagnostic tool in medicine. The most familiar examples are electrocardiography (ECG) and electro encephalography (EEG). Electrocardiograms, obtained by attaching electrodes to the chest and back and recording the regularly varying potential differences, are used to study heart function. Similarly, electrodes attached to the scalp permit study of potentials in the brain and the resulting patterns can be helpful in diagnosing epilepsy, brain tumors, and other disorders.

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    The most stable frequency can be generated using

  • Question 9
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    Directions For Questions

    The current in an LCRL-C-R series circuit fed by an alternating voltage source V=V0sinωtV =V_0\sin \omega t is given by
    i=V0sin(ωtϕ)R2+(Lω1Cω)2.....................(1)\displaystyle i = \dfrac{V_0\sin (\omega t - \phi)}{\sqrt{R^2 + \left(L\omega - \displaystyle \dfrac{1}{C\omega}\right)^2}}.....................(1)

    where tanϕ=ωL1ωCR.....................................(2)\displaystyle \tan\phi = \frac{\omega L- \dfrac{1}{\omega C}}{R} .....................................(2)

    ϕ\phi is the phase difference between the current and the voltage. The average power delivered by the source to the circuit is given by the equation 

    P=12V02cosϕZ\displaystyle P= \frac{1}{2} \frac{V_0^2 cos \phi}{|Z|}.........(3)

    Where |Z| is the impedance of the circuit given by the denominator of equation (1).

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    At resonance, the angle ϕ\phi is

  • Question 10
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    Directions For Questions

    In a series LCR circuit with an ideal ac source of peak voltage E0=50V{E}_{0}=50V, frequency v=50πv=\cfrac{50}{\pi} HzHz and R=300ΩR=300\Omega. The average electric field energy stored in the capacitor and average magnetic energy stored in the coil are 25mJ25mJ and 5mJ5mJ respectively. The value of RMS current in the circuit is 0.1A0.1A. Then find:

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    Capacitance (C)(C) of the capacitor is

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