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State the condition at which we say the two coils kept close to each other are perfectly coupled with each other.

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प्रश्न

State the condition at which we say the two coils kept close to each other are perfectly coupled with each other. 

एक पंक्ति में उत्तर
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उत्तर

When the coefficient of coupling (K) is 1, then the two coils kept close to each other are said to be perfectly coupled with each other. 

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अध्याय 12: Electromagnetic Induction - Very Short Answer

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संबंधित प्रश्न

Electric field intensity in free space at a distance ‘r’ outside the charged conducting sphere of radius ‘R’ in terms of surface charge density ‘ a ’ is............................

(a)`sigma / in_0[R/r]^2`

(b)`in_0/sigma[R/r]^2`

(c)`R/r[sigma/in_0]^2`

(d)`R/sigma[r/in_0]^2`

 


The magnetic flux through a loop varies according to the relation Φ = 8t2 + 6t + C, where ‘C’ is constant, 'Φ' is in milliweber and 't' is in second. What is the magnitude of induced e.m.f. in the loop at t = 2 seconds.


A solenoid of length 1.5 m and 4 cm in diameter possesses 10 turns per metre. A current of 5 A is flowing through it. The magnetic induction at a point inside the solenoid along the axis is ............................. .

0 = 4π × 10-7 Wb/Am)

  1. π  × 10-5 T
  2. 2π × 10-5 T
  3. 3π × 10-5 T
  4. 4π × 10-5 T

The device used for producing electric current is called _________.


A rectangular wire loop of sides 8 cm and 2 cm with a small cut is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cm s−1 in a direction normal to the

  1. longer side,
  2. shorter side of the loop? 

For how long does the induced voltage last in each case?


The magnetic flux through a loop is varying according to a relation `phi = 6t^2 + 7t + 1` where `phi` is in milliweber and t is in second. What is the e.m.f. induced in the loop at t = 2 second?


Prove theoretically  (electromagnetic induction) `e = (dphi)/(dt)`


If ‘R’ is the radius of dees and ‘B’ be the magnetic field of induction in which positive charges (q) of mass (m) escape from the cyclotron, then its maximum speed (vmax) is _______.

A) `(qR)/(Bm)`

B)`(qm)/(Br)`

C) `(qBR)/m`

D) `m/(qBR)`


A circular coil of cross-sectional area 200 cm2 and 20 turns is rotated about the vertical diameter with angular speed of 50 rad s−1 in a uniform magnetic field of magnitude 3.0 × 10−2T. Calculate the maximum value of the current in the coil.


The direction of current in the coil at one end of an electromagnet is clockwise. This end of the electromagnet will be:

(a) north pole
(b) east pole
(c) south pole
(d) west pole


When a wire is moved up and down in a magnetic field, a current is induced in the wire. What is this phenomenon known as?


When current is 'switched on' and 'switched off' in a coil, a current is induced in another coil kept near it. What is this phenomenon known as?


 What do you understand by the term "electromagnetic induction"? Explain with the help of a diagram. 


An induced current is produced when a magnet is moved into a coil. The magnitude of induced current does not depend on:  

(a) the speed with which the magnet is moved
(b) the number of turns of the coil
(c) the resistivity of the wire of the coil
(d) the strength of the magnet


In which of the following case does the electromagnetic induction occur?

A loop of wire is held near a magnet.


Show diagrammatically how an alternating emf is generated by a loop of wire rotating in a magnetic field. Write the expression for the instantaneous value of the emf induced in the rotating loop.


Electromagnetic induction means ______.


The coil of a moving-coil galvanometer keeps on oscillating for a long time if it is deflected and released. If the ends of the coil are connected together, the oscillation stops at once. Explain.


A conducting square loop of side l and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A uniform and constant magnetic field Bexists along the perpendicular to the plane of the loop as shown in figure. The current induced in the loop is _____________ .


A conducting rod is moved with a constant velocity v in a magnetic field. A potential difference appears across the two ends _____________ .


The switches in figure (a) and (b) are closed at t = 0 and reopened after a long time at t = t0.

(a) The charge on C just after t = 0 is εC.
(b) The charge on C long after t = 0 is εC.
(c) The current in L just before t = t0 is ε/R.
(d) The current in L long after t = t0 is ε/R.


Calculate the dimensions of (a) \[\int \overrightarrow{E} . d \overrightarrow{l,}\] (b) vBl and (c) \[\frac{d \Phi_B}{dt}.\] The symbols have their usual meaning.


Can you find the magnitude of current using Fleming's right hand rule?

State Fleming’s Right Hand Rule.


What is an electromagnet?


State the purpose of soft iron core used in making an electromagnet.


List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.


Why soft iron is preferred to be used as the core of the electromagnet of an electric bell?


What is an electromagnet? What do you know about the simplest form of an electromagnet?


You have been provided with a solenoid AB.

(i) What is the polarity at end A?
(ii) Give one advantage of an electromagnet over a permanent magnet.


Choose the correct option:

A conductor rod of length (l) is moving with velocity (v) in a direction normal to a uniform magnetic field (B). What will be the magnitude of induced emf produced between the ends of the moving conductor?


Observe the given figure of Fleming’s Right Hand Rule and write the labels of A and B correctly.


The right-hand thumb rule is also called _______ rule.


Which of the following scientist invented the rule of electromagnetic induction?


Give an illustration of determining direction of induced current by using Lenz’s law.


Obtain an expression for motional emf from Lorentz force.


A square coil of side 30 cm with 500 turns is kept in a uniform magnetic field of 0.4 T. The plane of the coil is inclined at an angle of 30° to the field. Calculate the magnetic flux through the coil.


A closely wound circular coil of radius 0.02 m is placed perpendicular to the magnetic field. When the magnetic field is changed from 8000 T to 2000 T in 6 s, an emf of 44 V is induced in it. Calculate the number of turns in the coil.


An alternating emf of 0.2 V is applied across an L-C-R series circuit having R = 4Q, C = 80µF, and L = 200 mH. At resonance the voltage drop across the inductor is


The laws of electromagnetic induction have been used in the construction of a ______.

Ansari Sir was demonstrating an experiment in his class with the setup as shown in the figure below.

A magnet is attached to a spring. The magnet can go in and out of the stationary coil. He lifted the Magnet and released it to make it oscillate through the coil.
Based on your understanding of the phenomenon, answer the following question.

What will be observed when the Magnet starts oscillating through the coil. Explain the reason behind this observation.


A galvanometer is an instrument that can detect the presence of a current in a circuit.


A conductor of length 50 cm carrying a current of 5 A is placed perpendicular to a magnetic field of induction 2×10 -3T. Find the force on the conductor.


The working of a dynamo is based on the principle of


AB is a coil of copper wire having a large number of turns. The ends of the coil are connected with a galvanometer as shown. When the north pole of a strong bar magnet is moved towards end B of the coil, a deflection is observed in the galvanometer.

  1. State the reason for using galvanometer in the activity and why does its needle deflects momentarily when magnet is moved towards the coil.
  2. What would be observed in the galvanometer in a situation when the coil and the bar magnet both move with the same speed in the same direction? Justify your answer.
  3. State the conclusion that can be drawn from this activity.
    Will there be any change in the momentary deflection in the galvanometer if number of turns in the coil is increased and a more stronger magnet is moved towards the coil?

OR

What is electromagnetic induction? What is observed in the galvanometer when a strong bar magnet is held stationary near one end of a coil of large number of turns? Justify your answer.


A conducting bar of length L is free to slide on two parallel conducting rails as shown in the figure

Two resistors R1 and R2 are connected across the ends of the rails. There is a uniform magnetic field `vec"B"` pointing into the page. An external agent pulls the bar to the left at a constant speed v. The correct statement about the directions of induced currents I1 and I2 flowing through R1 and R2 respectively is:


The charge will flow through a galvanometer of resistance 200Ω connected to a 400Ω circular coil of 1000 turns wound on a wooden stick 20 mm in diameter, if a magnetic field B = 0.012 T parallel to the axis of the stick decreased suddenly to zero, is near ______.


Show that for a given positive ion species in a cyclotron, (i) the radius of their circular path inside a dee is directly proportional to their speed, and (ii) the maximum ion energy achievable is directly proportional to the square of the magnetic induction.


Which type of force is experienced by a moving charge in a magnetic field?


A sheet is placed on horizontal surface in front of a strong magnetic pole. A force is needed to:

  1. hold the sheet there if it is magnetic.
  2. hold the sheet there if it is non-magnetic.
  3. move the sheet away from the pole with uniform velocity if it is conducting.
  4. move the sheet away from the pole with uniform velocity if it is both, non-conducting and nonpolar.

Choose the correct statement(s) from the options given below:


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