Objective Questions on Inductor | Page – 1

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  1. The unit of inductive susceptance is

    The unit of inductive susceptance is Simense. Susceptance (symbolized with B) is the opposite of reactance .Inductive susceptance becomes exactly like the formula for capacitive reactance, except that it of course uses inductance rather than capacitance.
    BL = 1 /( 2 X π X f X L).

  2. An inductor supplied with 100V with a frequency of 10 kHz and passes a current of 15.92 mA. The value of inductance is

    Here the supply voltage is 100V and current through the inductor is 15.92 mA
    ∴ impedance of the inductor is ZL = 100 / (15.92 X 10 - 3) Ω........(1)
    Expression for value of inductive impedance is given by ZL = 2π.f.L
    Here, frequency f = 10 KHz, hence, ZL = 2π.10000.L...........(2)
    Now, comparing, equation (1) and (2) we get, 100 / (15.92 X 10 - 3) = 2π.10000.L ⇒ L = 10 - 1 = 100 mH

  3. Which of the following case represents the largest mmf ?

    The mmf of any magnetic circuit is measured as a product of number of turns in the coil and current passing through that coil. Hence if I current flows through N number of turns in a coil the mmf will be N.I.

  4. A 100 mH inductor is connected across a supply for 50 V AC. For which of the following frequency the circuit will have least rms current?

    The impedance of a inductor is directly proportional to its supply frequency. RMS value of the current through the inductor is supply voltage/impedance. So, it can be concluded that current in inductor is inversely proportional to its supply frequency.

  5. A 200 mH inductor is connected across a supply for 100 V AC. For which of the following frequency the circuit will have highest rms current?

    The impedance of a inductor is directly proportional to its supply frequency. RMS value of the current through the inductor is supply voltage/impedance. So, it can be concluded that current in inductor is inversely proportional to its supply frequency.

  6. When ac flows through a pure inductance then the current

    When ac flows through an inductance, the current lags the emf by 900.

  7. The reactance of an inductor of 1 / π Henry at 50 Hz is

    Inductive reactance of an inductor is XL = 2π.f.L ΩHere, f = 50 Hz, L = 1 / π Henry. ∴ XL = 2π.50.(1 / π) Ω = 100 Ω

  8. The unit of inductance is Henry. It can also be represented as

    We know the induced voltage in an inductive circuit of inductance L, is V = Ldi/dt
    Where, L is proportional constant known as inductance
    From above expression we get, L = Vdt/di
    So, from above equation, it can be concluded that, unit of inductance henry is volt - sec /A

  9. The energy stored in an inductor of inductance L Henry is represented as,

    The voltage in an inductor is given as

  10. The instantaneous power in an inductor is proportional to the

  11. The voltage induced in an inductor of L Henry is represented as,

  12. Statement 1 :- Inductor doesn’t accept sudden changes in current.
    Statement 2 :- Inductor doesn’t accepts sudden changes in voltage.

    In order to accept sudden changes in current it requires infinite energy, infinite power and infinite voltage those are not desirable. So inductor doesn’t accept sudden changes in current.

  13. Which energy is stored in inductor and capacitor?

    The property of inductor is which stores magnetic field energy and electric field energy stored by capacitor.

  14. A circuit is having inductor, switch (initial at open) and it is connected to supply. After some time switch is closed then at time t=0+ how inductor behaves.

    In case of inductor current through it does not change instantaneously. If the initial conditions are zero, at the time of closing the switch for connecting an inductor to an energy source, the inductor will behave like an open circuit i.e.,no current will flow at t=0+.

  15. The strength of current in 1 Henry inductor changes at a rate of 2 A/sec. Find the voltage across it & determine the magnetic of energy stored in the inductor after 2 secs

    Here, L = 1 H, di/dt = 2 A/secs, voltage across the inductor, V = Ldi/dt = 1 X 2 = 2 V, The energy store (W) = ½L.I2 = ½ X 2 X 22 = 4 Joules.

  16. The switch is closed at time t=0, then the voltage across the inductor is given by

    At the time t=0+, inductor will acts as open circuit. Hence voltage across the inductor is Vo.

  17. Two inductances are in series their equivalent will be

    THE EQUIVALENT INDUACTANCE WHEN 2 INDUCTANCES ARE CONNECTED IN SERIES IS EQUAL TO THEIR SUM ALWAYS LIKE RESISTANCES.

  18. Property of pure inductor is

    Pure inductor only stores energy but donot dissipate it.

  19. The max value of mutual inductance of two inductively coupled coils with self inductance L1=49 mH & L2=81 mH

    M

  20. A coil has an inductive reactance of 4 ohm and a resistance of 3 ohm the admittance of the coil is

    Impedance, Z = 3 + i4 = √9+16 = 5
    Y = g -ib; g = R / Z2 = 3 / 52 = 0.12 ohm
    b = XL / Z2 = 4 / 52 = 0.16 ohm
    correct answer is 0.12 – i 0.16.

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