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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

Explain the phenomenon of self induction


Current in a circuit falls from 5.0 A to 0.0 A in 0.1 s. If an average emf of 200 V induced, give an estimate of the self-inductance of the circuit.


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


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 energies stored in the two coils at a given instant ?


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.


Define self inductance. Write its S.I. units.


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?


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 inductor-coil carries a steady-state current of 2.0 A when connected across an ideal battery of emf 4.0 V. If its inductance is 1.0 H, find the time constant of the circuit.


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.


What are the values of the self-induced emf in the circuit of the previous problem at the times indicated therein?


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. 


Choose the correct option

A current through a coil of self-inductance 10 mH increases from 0 to 1 A in 0.1 s. What is the induced emf in the coil?


Two pure inductors each of self-inductance L are connected in series, the net inductance is ______  


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


When a coil is connected to a D.C. source of e.m.f. 12 volt, then a current of 4 ampere flows in it. If the same coil is connected to a 12 volt, 25 cycle/s A.C sources, then the current flowing in it is 2.4 A. The self-inductance of the coil will be ______


Two rods of same material and volume having circular cross-section are subjected to tension T. Within the elastic limit, same force is applied to both the rods. Diameter of the first rod is half of the second rod, then the extensions of first rod to second rod will be in the ratio


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 ____________.


A toroidal solenoid with air core has an average radius 'R', number of turns 'N' and area of cross-section 'A'. The self-inductance of the solenoid is (Neglect the field variation cross-section of the toroid)


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


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 the current in a coil changes from 2 amp. to 4 amp. in 0.05 sec., an e.m.f. of 8 volt is induced in the coil. The coefficient of self inductance of the coil is ______.


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 ______.


A coil is wound on a frame of rectangular cross-section. If all the linear dimensions of the frame are increased by a factor 2 and the number of turns per unit length of the coil remains the same, self-inductance of the coil increases by a factor of ______.


The self-inductance associated with a coil is independent of ______.


An air-cored solenoid with length 30 cm, area of cross-section 25 cm2 and number of turns 800, carries a current of 2.5 A. The current is suddenly switched off in a brief time of 10-3s. Ignoring the variation in magnetic field near the ends of the solenoid, the average back emf induced across the ends of the open switch in the circuit would be ______.


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


What is the unit of self-inductance of a 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).


In a fluorescent lamp choke (a small transformer) 100 V of reverse voltage is produced when the choke current changes uniformly from 0.25 A to 0 in a duration of 0.025 ms. The self-inductance of the choke (in mH) is estimated to be ______.


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)


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.


Obtain an expression for the self inductance of a solenoid.


What is meant by magnetic coupling coefficient?


Two inductor coils with inductance 5 mH and 15 mH are connected in parallel. The resultant inductance of the combination of the two coils 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) versus `((dI)/(dt))`is shown graphically by:






What does \[L\] represent?


After whom is the SI unit henry (H) named?


What is the dimensional formula of self-inductance?


For a long solenoid of length \[l\] with \[N\] total turns, what is the number of turns per unit length?


What is the magnetic field inside a long air-core solenoid?


What is the magnetic flux through one turn of the long solenoid?


What is the self-inductance of a long air-core solenoid?


How does a magnetic core of relative permeability \[\mu_r\] change the solenoid self-inductance expression?


Which energy expression and field belong to a capacitor?


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