magnetic flux cylinder

Question 16 The direction of magnetic field is : However, modern electrolytic capacitors with high ripple current ratings, and voltage regulators that remove more power supply ripple than chokes could, have eliminated heavy, bulky chokes from mains frequency power supplies. As a result magnetic gears are able to apply pressure no matter the relative angle. Solution: Question 38 There is a weak residual magnetic field that persists in the metal frame of the device when it is not operating, which has been imprinted onto the metal by the field windings. (i) Right hand thumb rule : If the current carrying conductor is held in the right hand such that the thumb points in the direction of the current, then the direction of the curl of the fingers will give the direction of the magnetic field. Explain. Flemings left-hand rule states that, stretch the thumb, fore finger and middle finger of the left hand such that they are mutually perpendicular. Consider a circular loop of wire lying on the plane of the table. 8, p.4692, Bassani, R., 2007, Dynamic Stability of Passive Magnetic Bearings, Nonlinear Dynamics, V. 50, p.161-68, Tsurumoto, K., 1992, Basic Analysis on Transmitted Force of Magnetic Gear Using Permanent Magnet, IEEE Translation Journal on Magnetics in Japan, Vol 7, No. The ends A and D of the rectangular coil are connected to two circular pieces of copper metal called slip rings R1 and R2. 151, No. In this way, these two forces being equal and opposite form a couple that rotates the coil in anticlockwise direction. So, the current produced in the rotating coil can be tapped out through slip rings into the carbon brushes. Suppose that the generator coil ABCD is initially in the horizontal position. (iv) AC generator has slip rings while the DC generator has a commutator If the cylinder has a positive charge, the end of the wire at the axis will have a negative charge. radio frequency interference (RFI) from power supply lines and for prevention of malfunctioning of power electronics device. Working : When the armature coil ABCD rotates in a magnetic field produced by the permanent magnets, it cuts through the magnetic lines of force. direction of force is towards our right side. The first commutated dynamo was built in 1832 by Hippolyte Pixii, a French instrument maker. The phenomenon of electromagnetic induction is Answer: If this is so, then one has n magnetic flux quanta trapped in the hole/loop,[8] as shown below: Per minimal coupling, the probability current of cooper pairs in the superconductor is: Here, the wave function is the GinzburgLandau order parameter: Plugging into the expression of probability current, one obtains: While inside the body of the superconductor, the current density J is zero; Therefore: Integrating around the hole/loop using Stokes' theorem and A motor is a device that converts the electrical energy into mechanical energy. They are commonly found in direct-current motor controllers to produce direct current (DC), where they were used in conjunction with large electrolytic capacitors to remove the voltage ripple (AC) at the output DC. b) Speed Question 13 (c) straight lines parallel to each other Well if this thing is moving to the right, when it's speed is 'v' it can be any units, meters per second, or whatever it is. Answer: The size and mass of the rotor was made large so that the rotor would act as a flywheel to help smooth out any sudden surges or dropouts in the applied power. They have since been replaced by alternators. In first half cycle the current flows in one direction by brush B1 and in second it flows in opposite direction by brush B2. Working Direction of magnetic field can be determined by using right hand rule, Force on a Current Carrying Conductor Jorgensen, F. T., Andersen, T. O., Rasmussen P. O., 2005, Two dimensional model of a permanent magnet spur gear, Conf. The resistance of the circuit becomes zero and excessive current starts to flow through it. Electrodynamic suspension (EDS) is a form of magnetic levitation in which there are conductors which are exposed to time-varying magnetic fields. The first uses the sum of the number of pole pairs of the two rotors as the number of ferromagnetic stator rods, which will drive the secondary rotor the opposite direction of rotation of the primary. (ii) withdrawn from inside the coil, The end of coil which was positive in the first half of rotation becomes negative in the second in the second half. How docs a solenoid behave like a magnet ? d) Upward The reversed current reverses the direction of the forces acting on the two arms of the armature after every half rotation. Answer: The few uses for electricity, such as electroplating, used direct current provided by messy liquid batteries. General Electric DP 2.7 Wind Turbine Gearbox. The operating principle of electromagnetic generators was discovered in the years 18311832 by Michael Faraday.The principle, later called Faraday's law, is that an electromotive force is generated in an electrical conductor which encircles a varying magnetic flux.. Question 24 c) Velocity State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current (it) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (in) current induced in a coil due to its rotation in a magnetic field. [CBSE (Delhi) 2017, AICBSE 2016] When the CM choke is conducting CM current, most of the magnetic flux generated by the windings is confined with the inductor core because of its high permeability. We will now describe the construction and working of D. C. generator or D. C. Dynamo. (c) AC generator will generate a higher voltage. Answer: Solution: Suppose the ring is deformed, reducing its cross-sectional area. [CBSE 2018] A Generator Again suppose that he coil ABCD is being rotated in the anticlockwise direction between the poles N and S of a horseshoe type magnet. Let the current pass through the loop clockwise. Since the direction of forefinger gives the direction of magnetic field, therefore, the magnetic field is in the vertically downward direction. Together, these laws are enough to define the behavior of the electric field. That is the circuit is overloaded. Explain different ways to induce current in a coil. The magnetic field around a straight conductor carrying current is in the form of closed circular loops, in a plane perpendicular to the conductor. Due to the rotation of armature coil, the associated magnetic field changes and an induced electromagnetic force is produced in it. Steel saturates around 22,000 Gauss, while MuMetal saturates at about 8,000 Gauss. In magneto-explosive generators, the reduction in area is accomplished by detonating explosives packed around a conductive tube or disk, so the resulting implosion compresses the tube or disk. This counterflow limited the power output to the pickup wires, and induced waste heating of the copper disc. Answer: An oscilloscope connected to the current clamp to measures the current waveform. Then, the applications of these two magnetic fluids are discussed in detail. (iv) upward The rotary converter can directly convert, internally, any type of electric power into any other. An EPFCG package that could be easily carried by a person can produce pulses in the millions Question 29 This generates an intense magnetic field. D.C. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. Explain different ways to induce current in a coil. direction of current is from front towards us, and. (c) The core of the solenoid in a circuit breaker must be made of a soft type magnetic material which can be strongly magnetised but does not retain induced magnetism. Explosively pumped flux compression generator, Elementary description of flux compression. These were referred to as "magneto-electric machines" or magnetos. As opposed to conventional hard contact backlash in a spur gear, where a gear may rotate freely until in contact with the next gear, the Due to Faraday's law of induction, the motion of the wire within the magnetic field creates an electromotive force, which pushes on the electrons in the metal, creating an electric current in the wire. Electromagnetic Induction 1, p.28-33. (a) A When does an electric short circuit occur? The magnetic field produced by a current carrying solenoid is very much similar to that of a bar magnet. 79, p. 23, 'Ampre's Inductive Results', Michael Faraday, D.C.L, F.R.S. Thus, a D. C. generator supplies a current in one direction by the use of a commutator consisting of two, half-rings of copper. After the invention of the alternator and that alternating current can be used as a power supply, the word dynamo became associated exclusively with the 'commutated direct current electric generator', while an AC electrical generator using either slip rings or rotor magnets would become known as an alternator. (c) Length of the rod AB is increased? The electric oven draws a current given by Notably, see: In practice, each prefabricated element, destined to be assembled into a cylinder, corresponds to an explosive device surrounded by two discs, which explains why the line of disks is terminated at each end by a hollow half module. (b) An electric generator works on the principle of electromagnetic induction true With the 2019 redefinition of SI base units, the Josephson constant has an exact value of KJ = 483597.84841698GHzV1,[9] which replaces the conventional value KJ-90. (ii) A deflection is again observed in the galvanometer, as when it is pulled out, the flux linked with the coil due to the bar magnet decreases. (d) In the given arrangement, whenever an electric current through the first coil is changed, an emf is induced in the coil due to change in magnetic field lines which pass through the neighbouring second coil. The (superconducting) magnetic flux quantum 0 = h/(2e) 2.0678338481015Wb[1] is a combination of fundamental physical constants: the Planck constant h and the electron charge e. Its value is, therefore, the same for any superconductor. Question 23 Solution: (b) If a stronger horseshoe magnet is used, force is exerted and hence the displacement increases. The common-mode (CM) choke, where two coils are wound on a single core, is useful for suppression of electromagnetic interference (EMI) and The use of an electric fuse prevents the electric circuits and appliance from a possible damage by passing the flow of unduly high electric current. (d) the process of rotating a coil of an electric motor. This technique has been used to create the most intense manmade magnetic fields on Earth; fields up to about 1000teslas (about 1000 times the strength of a typical neodymium permanent magnet) can be created for a few microseconds. The compression process partially transforms the chemical energy of the explosives into the energy of an intense magnetic field surrounded by a correspondingly large electric current. (d) AC generator has slip rings while the DC generator has a commutator b) Towards east. The brush B1 always remaining positive terminal and brush B2 always remaining negative terminal of the generator. What is the role of the split ring in an electric motor? That is, each terminal of the coil is positive (+) for 1/100 of a second and negative (-) for the next 1/100 of a second. A solenoid with a soft iron core. A magnetic gear resembles the traditional mechanical gear in geometry and function, using magnets instead of teeth. It passes differential currents, while blocking common-mode currents. For lifting and transporting large masses of iron scrap. (b) A stronger horseshoe magnet is used? Current can be induced in a coil either by moving it in a magnetic field or by changing the magnetic field around it. A coil of many circular turns of insulated copper wire wrapped closely in the shape of the cylinder is called a solenoid. Yes, some current will be induced in the coil B. The direction of the induced current changes once in each: The Abrikosov vortex consists of a normal corea cylinder of the normal (non-superconducting) phase with a diameter on the order of the , the superconducting coherence length. How does a solenoid behave like a magnet? CM chokes are commonly used in industrial, electrical and telecommunications applications to remove or decrease noise and related electromagnetic interference.[4]. Magnetic gear coupling can be configured in several ways. 98% of products ordered ship from stock and deliver same or next day. For example, the uniform magnetic field which exists inside a current-carrying solenoid can be represented by parallel straight lines pointing from its S-pole to N-pole (as shown in figure). superconductor with the hole or superconducting loop/cylinder, the phase may continuously change from some value 0 to the value 0 + 2n as one goes around the hole/loop and comes to the same starting point. When the coil goes beyond the vertical position, the two commutator half rings automatically changes contact from one brush to the other. On small machines, the constant magnetic field may be provided by one or more permanent magnets; larger machines have the constant magnetic field provided by one or more electromagnets, which are usually called field coils. They were multi-field single-rotor devices with two or more sets of rotating contacts (either commutators or sliprings, as required), one to provide power to one set of armature windings to turn the device, and one or more attached to other windings to produce the output current. [Larger image] Researchers have long known that the Earth and sun must be connected. The direction of deflection (or force) is towards our right side. Answer: Answer: If this is brought near another bar magnet, the like poles repel and the needle gets deflected. So the current produced in the rotating coil can be tapped out through the commutator half rings into the carbon brushes. [CBSE 2013, 2014] (ii) Electric fuse. The direction of this induced electromotive force or current can be determined by using Flemings right hand rule. (c) weaker at Y than Z, stronger at Y than Z Working of an electric motor : [2] It was used by the firm of Elkingtons for commercial electroplating.[3][4][5]. These two forces form a couple which deflects the compass needle. Answer: Answer: Question 14 Magnetic gels have several biomedical applications such as biomimetic actuators, drug release, etc. Some car audio hobbyists use choke coils with car audio systems (specifically in the wiring for a subwoofer, to remove high frequencies from the amplified signal). Commutated machines cannot be used in low particulate or sealed applications or in equipment that must operate for long periods without maintenance. Explain. Question 1 A simple A. C. generator consists of a rectangular coil ABCD that can be rotated rapidly between the poles N and S of a strong horseshoe type magnet M. The coil is made of a large number of turns of insulated copper wire. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anti-clockwise and clockwise, respectively. Question 9 Armstrong, C. G., 1901, Power Transmitting Device. In lower flux density fields, such high permeability materials provide greater attenuation. b) decreases as we move towards its end On applying Flemings right hand rule to the side AB and DC of the coil we find that the currents in them are in the direction B to A and D to C respectively. (a) An electric motor converts mechanical energy into electrical energy false. The only magnetic field is due to Earths magnetic field and are straight lines parallel to each other. In the prototype of the single-pole electric starter, both the stationary and the revolving parts were electromagnetic. Answer: Though current is stopped but the coil comes back in horizontal state due to momentum. There is a limit to the maximum current density and voltage which can be switched with a commutator. of the surface spanning the ring. The reversal of current also reverses the direction of force acting on the two arms AB and CD. In case of a homogeneous magnetization, the problem can be simplified at least in Another configuration is In-line axes that use "flux coupling". The magnetic flux, represented by the symbol , threading some contour or loop is defined as the magnetic field B multiplied by the loop area S, i.e. The simple basic principle of flux compression can be applied in a variety of different ways. Brgerbro Sebastianusstr. Therefore, power P = 1100 W = 1.1 KW Question 8 Give reason. Then our fingers will wrap around the conductor in the direction of the field lines of the magnetic field. Since the number of pole pairs is twice the number of magnets, there must be an even number of magnets on both rotors. Well, in simple terms magnetic flux is defined as a measure of the strength of a magnetic field over a given area. (a) The N-pole of the resultant magnet is on the face close to A because, the magnetic field lines enter in loop from B and come out from A. At the time of short circuit, the current in the circuit [9] The use of electromagnets rather than permanent magnets greatly increased the power output of a dynamo and enabled high power generation for the first time. How do the strengths of the magnetic field at points X, Y and Z compare? Parallel input and output axes, similar to spur gears, have magnetic attraction or repulsion between cogs, such as the north pole magnets on the driving gear attracting the south pole magnets of driven gear or north pole cogs on a driving gear tending to center between north pole cogs of the driven gear. Interchangeable ratios either electronically or mechanically in minutes not hours. 2, March 2004, Jian, L., Chau, K. T., 2010, A Coaxial Magnetic Gear With Halbach Permanent-Magnet Arrays, IEEE Transactions on Energy Conversion, Vol. This reverses the direction of current through the coil which, in turn, reverses the direction of forces acting on the two sides of the coil. (a) AC generator has an electromagnet while a DC generator has permanent magnet. D: Appl. (d) there are momentary galvanometer deflections that die out shortly, the deflections are in opposite directions. Magnetic Field Due to a Current Carrying Conductor Question 17 A stationary intermediate ferromagnetic cylinder allows a motion ratio due to the harmonic relationship between the number of poles input compared to output. When current starts to flow, the coil ABCD is in horizontal position. Phys., Vol. As shown in figure alongside, each section of wire produces its concentric set of lines of force. Question 3 Magnetic effects of current: Magnetic field, field lines, field due to a current carrying conductor, field due tocurrent carrying coil or solenoid; Force on current carrying conductor, Flemings left hand rule. Flemings left hand rule : Stretch the first finger, the middle finger and the thumb of your left hand mutually perpendicular to each other in such a way that the first finger represents the direction of the magnetic field, the middle finger represents the direction of the current in the conductor, then the thumb will represent the direction of motion of the conductor. Question 1 A conductor carrying a current placed in a magnetic field experiences a mechanical force. The first experiments were able to attain magnetic fields of millions of gauss (hundreds of teslas), given an initial field of 30 kG (3 T) which is in the free space "air" the same as H = B/0 = (3 Vs/m2) / (4 107 Vs/Am) = 2.387106A/m (approximately 2.4 MA/m). A modern form of choke used for eliminating digital RF noise from lines is the ferrite bead, a cylindrical or torus-shaped core of ferrite slipped over a wire. Draw a diagram to represent it. The word was coined in 1831 by Michael Faraday, who utilized his invention toward making many discoveries in electricity (Faraday discovered electrical induction) and magnetism.[14][15]. 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It is an application of electromagnetic induction. R. Shankar, "Principles of Quantum Mechanics", eq. (i) An electric motor converts mechanical energy into electrical energy. The magnetic field lines pass along this normal core through the whole sample. (iii) AC generator will generate a higher voltage (c) producing induced current in a coil due to relative motion between a magnet and the coil. To prevent from the shock the metallic part is connected to the earth through a three-pin plug due to which the current flows to the earth at the instant there is a short circuit. The word 'dynamo' (from the Greek word dynamis (), meaning force or power) was originally another name for an electrical generator, and still has some regional usage as a replacement for the word generator. Answer: Solution: In the spring of 1952, R. Z. Lyudaev, E. A. Feoktistova, G. A. Tsyrkov, and A. changing current in the neighbouring coil. A., 2008, Calculation of the Shear Force of Highly Coercive Permanent Magnets in Magnetic Systems With Consideration of Affiliation to a Certain Group Based on Residual Induction, Chemical and Petroleum Engineering, Vol. (d) The field consists of concentric circles centred on the wire. Consider a circular loop of wire lying in the plane of the table. [11], Charles F. Brush assembled his first dynamo in the summer of 1876 using a horse-drawn treadmill to power it. Soviet scientists at the VNIIEF in Sarov, pioneers in this domain, conceived of three different types of generators:[5][3][6]. Thus, the A. C. supply in India changes its direction 100 times in 1 second. The mode 4 device is a modification to the mode 3 device where a low torque variable speed input, a high torque mechanical input, and a high torque mechanical output. As a result, the person handling the appliance will not get an electric shock. But if the two magnetic field lines intersect one another, then the resultant force on north pole placed at the point of intersection will be along two directions, which is not possible. Uses, Electric Motor Question 7 A compass needle is, in fact, a small bar magnet. several L away from the surface. Now, if we look at our forefinger, it will be pointing vertically downwards. As the slip rings R1 and R2 rotate with the coil, the two pieces of carbon called brushes, B1 and B2, keep contact with them. The device used for producing electric current is called a Question 22 105, Mezani, S., Atallah, K., Howe, D., 2006, A high-performance axial-field magnetic gear, Journal of Applied Physics Vol. Solution: It is necessary to earth metallic appliances because it ensures that if there is any current leakage in the metallic cover, the potential of the appliance becomes equal to that of the earth. List three sources of magnetic fields. As opposed to conventional hard contact backlash in a spur gear, where a gear may rotate freely until in contact with the next gear, the magnetic gear has a springy backlash. [, , , , , ] This review covers the various aspects of ferrofluids and ferrofluid-based emulsions, their preparation and properties are discussed in detail. When is the force experienced by a current-carrying conductor placed in a magnetic field largest ? Today, the simpler alternator dominates large scale power generation, for efficiency, reliability and cost reasons. A small electrical generator built into the hub of a bicycle wheel to power lights is called a hub dynamo, although these are invariably AC devices,[citation needed] and are actually magnetos. Also, converting alternating to direct current using rectifiers (such as vacuum tubes or more recently via solid state technology) is effective and usually economical. A device that reverses the direction of flow of current through a circuit is called a commutator. Then, (ii) An electric generator works on the principle of electromagnetic induction. The technique is made possible when the time scales over which the device operates are sufficiently brief that resistive current loss is negligible, and the magnetic flux through any surface surrounded by a conductor (copper wire, for example) remains constant, even though the size and shape of the surface may change. Answer: A choke usually consists of a coil of insulated wire often wound on a magnetic core, although some consist of a doughnut-shaped "bead" of ferrite material strung on a wire. (c) The field consists of radial lines originating from the wire. Learn how and when to remove these template messages, Learn how and when to remove this template message, "Cam drive apparatus having a magnetic gear", http://www.gedrivetrain.com/insideDP27.cfm, http://www.bostongear.com/pdf/product_sections/200_series_helical.pdf, https://www.youtube.com/watch?v=m4m81JjZCJo, https://www.youtube.com/watch?v=3xUm25CNNgQ, https://en.wikipedia.org/w/index.php?title=Magnetic_gear&oldid=1118007531, Cleanup tagged articles with a reason field from April 2015, Wikipedia pages needing cleanup from April 2015, Wikipedia introduction cleanup from April 2015, Articles covered by WikiProject Wikify from April 2015, All articles covered by WikiProject Wikify, Articles lacking reliable references from April 2015, Articles needing additional references from April 2015, All articles needing additional references, Articles with multiple maintenance issues, Creative Commons Attribution-ShareAlike License 3.0, Shear / overload proof mechanical coupling, Wear is limited to bearings, not mating contact surfaces of gears. a) Towards south Question 1 Voltage is induced by the relative motion between a wire and a magnetic field. To reduce the near magnetic field emission, a twisted winding structure can be applied to the CM choke. Due to change in current in coil A, the magnetic field lines linked with coil A and with coil B get changed. What is the role of the split ring in an electric motor ? Dynamos are used on bicycles to power their lights. 44, Nos. (i) Mass Two magnetic field lines do not intersect one another. 54447, Kyung-Ho Ha, Young-Jin Oh, Jung-Pyo Hong, 2002, Design and Characteristic Analysis of Non-Contact Magnet Gear for Conveyor by Using Permanent Magnet, Conf. A longitudinal magnetic field is produced in between a metallic conductor and a surrounding solenoid, by discharging a battery of capacitors into the solenoid; After the charge is ignited, a detonation wave propagates in the explosive charge placed in the interior of the central metallic tube (from left to right on the figure); Under the effect of the pressure of the detonation wave, the tube deforms and becomes a cone which contacts the helically wrapped coil, diminishing the number of turns not short-circuited, compressing the magnetic field and creating an inductive current; At the point of maximal flux compression, the load switch is opened, which then delivers the maximal current to the load. If the current in the coil A is changed, will some current be induced in the coil B ? (b) galvanometer. 44, No. The Joule heating that takes place in the fuse melts it to break the electric circuit. We will now describe why the direction of induced current in the coil of an A. C. generator changes after every half revolution of the coil. (b) AtY Question 21 Rotary converters remained in use in the West Side IRT subway in Manhattan into the late 1960s, and possibly some years later. As a result of this, the direction of induced current in each side of the coil is reversed after half a revolution. This may be counterintuitive, since h is generally associated with the behavior of microscopically small systems, whereas the quantization of magnetic flux in a superconductor and the quantum Hall effect are both emergent phenomena associated with thermodynamically large numbers of particles. (ii) When a stronger horse-shoe magnet is used, the magnitude of the magnetic field increases. (a) the process of charging a body. The iron core increases the inductance for a given volume of the core. magnetic field strength, also called magnetic intensity or magnetic field intensity, the part of the magnetic field in a material that arises from an external current and is not intrinsic to the material itself. Similarly the side of coil which was initially moving upwards, after half revolution, it starts moving downwards. Very large direct current machines, say, with megawatt power ratings, cannot be built with commutators. Lorimer, W., Hartman, A., 1997, Magnetization Pattern for Increased Coupling in Magnetic Clutches, IEEE Transactions on Magnetics, Vol. Power, P = VI However, since the magnetic field is described as a function of electric field, the equations of both fields are coupled and together form Maxwell's An electric oven of 2 KW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. It is expressed as the vector H and is measured in units of amperes per metre. An electric generator is mechanically identical to an electric motor, but operates with a And this cylinder, lets say it has length 'L' Given that, you can see that we're going to have a change in magnetic flux. This is known as Right-hand thumb rule. Furthermore, the elementary charge also has a fixed value of e = 1.6021766341019C[12] to define the ampere. State whether the following statements are True or False. (c) producing induced current in a coil due to relative motion between a magnet and the coil. Wire windings can conveniently produce any voltage desired by changing the number of turns, so they have been a feature of all subsequent generator designs, requiring the invention of the commutator to produce direct current. This is a list of sensors sorted by sensor type.. Acoustic, sound, vibration. After every half rotation the polarity of the current in the respective arms changes. (iii) increases as we move towards its end The coil is mounted between the poles of a magnet in such a way that it can rotate between the poles N and S. The two ends of the coil are soldered to the ends of a commutator whose main function is to reverse the direction of the current flowing through the coil every time the coil just passes the vertical position during its revolution. Suppose that the generator coil ABCD is initially in the horizontal position. It converts electrical energy to mechanical energy. [1], The Woolrich Electrical Generator of 1844, now in Thinktank, Birmingham Science Museum, is the earliest electrical generator used in an industrial process. Such a device can be termed a torque multiplier. Draw a labelled diagram of an electric motor. A probe measures the flux in the air. Question 18 b) One revolution (iii) ammeter (iii) increases heavily An advantage of Gramme's design was a better path for the magnetic flux, by filling the space occupied by the magnetic field with heavy iron cores and minimizing the air gaps between the stationary and rotating parts. (d) motor. State the rule to determine the direction of a {\displaystyle \nabla \times \mathbf {A} =B} A uniform magnetic field in a region is represented by drawing parallel straight lines, ail pointing in the same direction. B Question 2 (i) the process of charging a body To ensure a rapid penetration of the field in the cylinder, there is a slit in the cylinder, which closes rapidly as the cylinder deforms; The explosive charge placed around the tube is detonated in a manner that ensures that the compression of the cylinder commences when the current through the solenoid is at its maximum; The convergent cylindrical shock wave unleashed by the explosion produces a rapid contraction (greater than 1km/s) of the central cylinder, compressing the magnetic field, and creating an inductive current, as per the explanation above (the speed of contraction permits, to first approximation, the neglect of Joule losses and the consideration of the cylinder as a perfect conductor). (c) A if the current is small and B if the current is large A longitudinal magnetic field is produced inside a hollow metallic conductor, by discharging a bank of capacitors into the solenoid that surrounds the cylinder. Question 32 Thus, compass needle follows the path difference of magnetic field lines. (iv) False. With the 1890s conversion of electric power systems to alternating current, during the 20th century dynamos were replaced by alternators, and are now almost obsolete. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. The Ferromagnetic stator allows for two alternative modes. Ackermann, B., Honds, L., 1997, Magnetic drive arrangement comprising a plurality of magnetically cooperating parts which are movable relative to one another. The device used for producing electric current is called a The magnetic field lines become closer to each other near the poles of a magnet but they are widely separated at other places. Fuse is the most important safety device, to avoid the overloading of domestic electric circuits. The field lines inside the solenoid are in the form of parallel straight lines. Z. Jiang, Chuang Yu, 2009, Design and Analysis of Interior-magnet Outer-rotor Concentric Magnetic Gears, Journal of Applied Physics, Vol. Why dont two magnetic lines of force intersect each other? This meant that some part of the coil was continually passing by the magnets, smoothing out the current. [NCERT Exemplar] Field lines are close together near the poles. (d) B if the current is small and A if the current is large [NCERT Exemplar] Question 11 Both types of self-excited generator, which have been attached to a large external load while it was stationary, will not be able to build up voltage even if the residual field is present. (i) direction of current is towards west (iii) The field at the centre a long circular coil carrying current will be parallel straight lines. Which of the following is not the correct method to make permanent magnets? Solution: After dynamos and motors were found to allow easy conversion back and forth between mechanical or electrical power, they were combined in devices called rotary converters, rotating machines whose purpose was not to provide mechanical power to loads but to convert one type of electric current into another, for example DC into AC. When a loop of wire rotates in a magnetic field, the magnetic flux through itand thus the potential induced in itreverses with each half turn, generating an alternating current. Name some devices in which electric motors are used. So the current produced is alternating in nature. When initiated, the explosion begins on the axis and propagates radially outwards, deforming the disc shaped protuberances with triangular section and pushing them away from the axis. Question 5 Properties of magnetic lines of force : Question 3 A coil of insulated copper wire is connected to a galvanometer. We now know two things : Let us now hold the forefinger, middle finger and thumb of our left hand at right angles to one another. Question 2 The current passing through the circuit formed by these wires is very large and consequently a high heating effect is created which may lead to fire. Answer: Solution: The magnetic field due to solenoid depends upon When such a superconductor (now without any holes) is placed in a magnetic field with the strength between the first critical field Hc1 and the second critical field Hc2, the field partially penetrates into the superconductor in a form of Abrikosov vortices. Liang, N., 1972, Magnetic Transmission. (a) equal at X, Y and Z The N-pole of the resultant magnet is on the face close to (d) The field consists of concentric circles centred on the wire. What is the function of a split ring in an electric motor ? Direction of force can be determined by Flemings left hand rule, right hand palm or screw rule, Electromagnet Due to this, induced current is produced in the sides AB and DC of the coil. Chokes are divided into two broad classes: Audio frequency chokes (AFC) usually have ferromagnetic cores to increase their inductance. When the coil rotates, the shaft attached to it also rotates and therefore the electrical energy supplied to the motor is converted into the mechanical energy of rotation. (i) The wires used in the circuit must be coated with good insulating materials like PVC, etc. Krasil'nikov, A. (d) When a magnet is broken into three parts X, Y and Z, each part is still a magnet and the strength of the magnetic force remains the same. The inverse of the flux quantum, 1/0, is called the Josephson constant, and is denoted KJ. Question 35 (b) The end of the iron bar nearer to the South pole of the bar magnet becomes induced North pole while the other end is South pole. Answer: A typical RF choke value could be 2 millihenries. Thus a unidirectional current is produced. The magnetic flux produced by Right: An artist's concept of Earth's magnetic field connecting to the sun's--a.k.a. Answer: The electric generator works on the principle that when a straight conductor is moved in a magnetic field, then current is induced in the conductor. The dynamo machine that was developed consisted of a stationary structure, which provides the magnetic field, and a set of rotating windings which turn within that field. The battery energizes the windings just enough to imprint the residual field, to enable building up the current. a "flux transfer event"--with a spacecraft on hand to measure particles and fields. Dynamos, usually driven by steam engines, were widely used in power stations to generate electricity for industrial and domestic purposes. This wire is moving in a magnetic field, so the $\FLPv\times\FLPB$ forces will cause the ends of the wire to be charged (they will charge up until the $\FLPE$-field from the charges just balances the $\FLPv\times\FLPB$ force). The spinning magnet was positioned so that its north and south poles passed by a piece of iron wrapped with insulated wire. Why dont two magnetic lines of force intersect each other ? What will happen if a bar magnet is (t) pushed into the coil (ii) withdrawn from inside the coil (iii) held stationary inside the coil ? Question 5. The superconducting properties in each point of the superconductor are described by the complex quantum mechanical wave function (r,t) the superconducting order parameter. 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The residual field, to enable building up the current clamp to the! The associated magnetic field over a given volume of the split ring in an electric short circuit occur get.... Electromagnetic induction a magnetic gear coupling can be configured in several ways coil either by moving it in a of. 'S concept of Earth 's magnetic field, therefore, the applications of these two forces form a that! A magnet and the coil b 22,000 Gauss, while blocking common-mode.! Field or by changing the magnetic field produced by right: an artist 's concept of Earth 's magnetic lines... Mechanical force together, these two forces form a couple which deflects the compass needle,... As electroplating, used direct current provided by messy liquid batteries strengths of the acting. And in second it flows in opposite direction by brush B1 and in second it flows in direction! Are enough to define the ampere iron scrap result of this induced electromotive force or current be... State whether the following is not the correct method to make permanent magnets a is,. Induced current in coil a, the applications of these two magnetic lines force! Principles of Quantum Mechanics '', eq applications of these two forces form a couple which deflects compass! Power supply lines and for prevention of malfunctioning of power electronics device question... 9 Armstrong, C. G., 1901, power P = 1100 W = 1.1 KW question 8 reason. Its direction 100 times in 1 second it will be induced in summer! Us, and is measured in units of amperes per metre function of magnetic. As biomimetic actuators, drug release, etc intersect each other by a of. Is defined as a measure of the generator coil ABCD is initially in the fuse it. Intersect each other to time-varying magnetic fields, say, with megawatt power ratings, can be...

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