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महाराष्ट्र राज्य शिक्षण मंडळएचएससी विज्ञान (सामान्य) इयत्ता १२ वी

Explain why the inductance of two coils connected in parallel is less than the inductance of either coil.

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प्रश्न

Explain why the inductance of two coils connected in parallel is less than the inductance of either coil.

टीपा लिहा
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उत्तर १

  1. For a parallel combination of two coils, the current through each parallel inductor is a fraction of the total current and the voltage across each parallel inductor is the same.
  2. As a result, a change in total current will result in less voltage dropped across the parallel array than for any one of the individual inductors.
  3. There will be less voltage drop across parallel inductors for a given rate of change in current than for any of the individual inductors.
  4. Less voltage for the same rate of change in current results in less inductance.
  5. Thus, the total inductance of two coils is less than the inductance of either coil.
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उत्तर २

When two inductors with inductances L1 and L2 are connected in parallel, the equivalent inductance is given by

`1/"L"_"equivalent" = 1/"L"_1 + 1/"L"_2`

which is less than the individual inductance value L1 and L2.

As a result, the inductance of two parallel coils is smaller than the inductance of either coil.

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  या प्रश्नात किंवा उत्तरात काही त्रुटी आहे का?
पाठ 12: Electromagnetic Induction - Short Answer I

संबंधित प्रश्‍न

In a given coil of self-inductance of 5 mH, current changes from 4 A to 1 A in 30 ms. Calculate the emf induced in the coil.


Define the coefficient of self-induction.


Write the SI unit and dimention of of co-efficient of self induction


Define self-inductance. Write its SI units.


The currents flowing in the two coils of self-inductance L1 = 16 mH and L2 = 12 mH are increasing at the same rate. If the power supplied to the two coil is equal, find the ratio of induced voltages ?


The currents flowing in the two coils of self-inductance L1 = 16 mH and L2 = 12 mH are increasing at the same rate. If the power supplied to the two coil is equal, find the ratio of  the currents ?


Define self-inductance of a coil. Show that magnetic energy required to build up the current I in a coil of self inductance L is given by `1/2 LI^2`


Derive the expression for the self-inductance of a long solenoid of cross sectional area A and length l, having n turns per unit length.


Derive an expression for self inductance of a long solenoid of length l, cross-sectional area A having N number of turns.


Consider the self-inductance per unit length of a solenoid at its centre and that near its ends. Which of the two is greater?


A constant current i is maintained in a solenoid. Which of the following quantities will increase if an iron rod is inserted in the solenoid along its axis?
(a) magnetic field at the centre
(b) magnetic flux linked with the solenoid
(c) self-inductance of the solenoid
(d) rate of Joule heating.


Two solenoids have identical geometrical construction but one is made of thick wire and the other of thin wire. Which of the following quantities are different for the two solenoids?

(a) self-inductance
(b) rate of Joule heating if the same current goes through them
(c) magnetic field energy if the same current goes through them
(d) time constant if one solenoid is connected to one battery and the other is connected to another battery.


An average emf of 20 V is induced in an inductor when the current in it is changed from 2.5 A in one direction to the same value in the opposite direction in 0.1 s. Find the self-inductance of the inductor.


A coil having inductance 2.0 H and resistance 20 Ω is connected to a battery of emf 4.0 V. Find (a) the current at the instant 0.20 s after the connection is made and (b) the magnetic field energy at this instant.


An inductor of inductance 5.0 H, having a negligible resistance, is connected in series with a 100 Ω resistor and a battery of emf 2.0 V. Find the potential difference across the resistor 20 ms after the circuit is switched on.


Consider a small cube of volume 1 mm3 at the centre of a circular loop of radius 10 cm carrying a current of 4 A. Find the magnetic energy stored inside the cube.


Answer the following question.
When an inductor is connected to a 200 V dc voltage, a current at 1A flows through it. When the same inductor is connected to a 200 V, 50 Hz ac source, only 0.5 A current flows. Explain, why? Also, calculate the self-inductance of the inductor. 


A coil of self-inductance 3 H carries a steady current of 2 A. What is the energy stored in the magnetic field of the coil? 


Define self-inductance.


Obtain an expression for the self-inductance of a solenoid.


The coefficient of self-inductance of a solenoid is 0.20 mH. If a core of soft iron of relative permeability 900 is inserted, then the coefficient of self-inductance will become nearly ______


The magnetic potential energy stored in a certain inductor is 15 mJ, when the current in the inductor is 40 mA. This inductor is of inductance ____________.


Consider a solenoid carrying supplied by a source with a constant emf containing iron core inside it. When the core is pulled out of the solenoid, the change in current will ______.


An e.m.f. of 10 volt is produced by a self inductance when the current changes at a steady rate from 6 A to 4 A in 1 millisecond. The value of self inductance is ____________.


Two coils of wire A and B are placed mutually perpendicular as shown. When current is changed in any one coil.


A resistance of 100 `Omega`, inductor of self-inductance`(4/pi^2)` H and a capacitor of unknown capacitance are connected in series to an a.c. source of 200 V and 50 Hz. When the current and voltage are in phase, the capacitance and power dissipated is respectively ____________.


A graph of magnetic flux `(phi)` versus current (I) is shown for four inductors A, B, C and D. Larger value of self-inductance is for inductor ____________.


When current i passes through an inductor of self-inductance L, energy stored in it is 1/2. L i2. This is stored in the ______.


The self-inductance of a coil is a measure of ______.

If both the number of turns and core length of an inductor is doubled keeping other factors constant, then its self-inductance will be ______.


Energy needed to establish an alternating current I in a coil of self-inductance L is


An inductor may store energy in


What is the unit of self-inductance of a coil?


A coil of wire of a certain radius has 600 turns and a self-inductance is 108 mH. The self-inductance of a second similar coil of 500 turns will be:


An average induced emf of 0.20 V appears in a coil when the current in it is changed from 5A in one direction to 5A in the opposite direction in 0.20 sec. Find the self induction of the coil.


Consider an infinitely long wire carrying a current I(t), with `(dI)/(dt) = λ` = constant. Find the current produced in the rectangular loop of wire ABCD if its resistance is R (Figure).


The inductance of a solenoid L having diameter d. Let n be the number of turns per unit length. The inductance per unit length near the middle of a solenoid is ______.

(Assume that, l = current passes through the turns, µ0 = Permeability of vacuum)


Calculate the self-inductance of a coil using the following data obtained when an AC source of frequency `(200/pi)` Hz and a DC source are applied across the coil.

AC Source
S.No. V (volts) I (A)
1 3.0 0.5
2 6.0 1.0
3 9.0 1.5
DC Source
S.No. V (volts) I (A)
1 4.0 1.0
2 6.0 1.5
3 8.0 2.0

A current of 1A flows through a coil when it is connected across a DC battery of 100V. If the DC battery is replaced by an AC source of 100 V and angular frequency of 100 rad s-1, the current reduces to 0.5 A. Find

  1. the impedance of the circuit.
  2. self-inductance of coil.
  3. Phase difference between the voltage and the current.

An air-cored solenoid, 40 cm long and of cross-sectional area 5 cm2, is tightly wound with 400 turns of copper wire and carries a steady current of 10 A. (a) Calculate the self-inductance of the solenoid. (b) Find the emf induced if the current in the solenoid decreases to zero in 0.2 s.


State the factors on which the magnetic coupling coefficient of two coils depends.


What is meant by magnetic coupling coefficient?


The current in a coil changes from 50A to 10A in 0.1 second. The self inductance of the coil is 20H. The induced e.m.f. in the coil is ______.


The current flowing through an inductor of self-inductance L is continuously increasing at constant rate. The variation of induced e.m.f. (e) verses dI/dt is shown graphically by figure


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