If the current in the core decreases; what will the strength of the magnetic field be? ?->(Show Answer!)

1. If the current in the core decreases; what will the strength of the magnetic field be?

Answer: Decreases

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MCQ-> In a modern computer, electronic and magnetic storage technologies play complementary roles. Electronic memory chips are fast but volatile (their contents are lost when the computer is unplugged). Magnetic tapes and hard disks are slower, but have the advantage that they are non-volatile, so that they can be used to store software and documents even when the power is off.In laboratories around the world, however, researchers are hoping to achieve the best of both worlds. They are trying to build magnetic memory chips that could be used in place of today’s electronics. These magnetic memories would be nonvolatile; but they would also he faster, would consume less power, and would be able to stand up to hazardous environments more easily. Such chips would have obvious applications in storage cards for digital cameras and music- players; they would enable handheld and laptop computers to boot up more quickly and to operate for longer; they would allow desktop computers to run faster; they would doubtless have military and space-faring advantages too. But although the theory behind them looks solid, there are tricky practical problems and need to be overcome.Two different approaches, based on different magnetic phenomena, are being pursued. The first, being investigated by Gary Prinz and his colleagues at the Naval Research Laboratory (NRL) in Washington, D.c), exploits the fact that the electrical resistance of some materials changes in the presence of magnetic field— a phenomenon known as magneto- resistance. For some multi-layered materials this effect is particularly powerful and is, accordingly, called “giant” magneto-resistance (GMR). Since 1997, the exploitation of GMR has made cheap multi-gigabyte hard disks commonplace. The magnetic orientations of the magnetised spots on the surface of a spinning disk are detected by measuring the changes they induce in the resistance of a tiny sensor. This technique is so sensitive that it means the spots can be made smaller and packed closer together than was previously possible, thus increasing the capacity and reducing the size and cost of a disk drive. Dr. Prinz and his colleagues are now exploiting the same phenomenon on the surface of memory chips, rather spinning disks. In a conventional memory chip, each binary digit (bit) of data is represented using a capacitor-reservoir of electrical charge that is either empty or fill -to represent a zero or a one. In the NRL’s magnetic design, by contrast, each bit is stored in a magnetic element in the form of a vertical pillar of magnetisable material. A matrix of wires passing above and below the elements allows each to be magnetised, either clockwise or anti-clockwise, to represent zero or one. Another set of wires allows current to pass through any particular element. By measuring an element’s resistance you can determine its magnetic orientation, and hence whether it is storing a zero or a one. Since the elements retain their magnetic orientation even when the power is off, the result is non-volatile memory. Unlike the elements of an electronic memory, a magnetic memory’s elements are not easily disrupted by radiation. And compared with electronic memories, whose capacitors need constant topping up, magnetic memories are simpler and consume less power. The NRL researchers plan to commercialise their device through a company called Non-V olatile Electronics, which recently began work on the necessary processing and fabrication techniques. But it will be some years before the first chips roll off the production line.Most attention in the field in focused on an alternative approach based on magnetic tunnel-junctions (MTJs), which are being investigated by researchers at chipmakers such as IBM, Motorola, Siemens and Hewlett-Packard. IBM’s research team, led by Stuart Parkin, has already created a 500-element working prototype that operates at 20 times the speed of conventional memory chips and consumes 1% of the power. Each element consists of a sandwich of two layers of magnetisable material separated by a barrier of aluminium oxide just four or five atoms thick. The polarisation of lower magnetisable layer is fixed in one direction, but that of the upper layer can be set (again, by passing a current through a matrix of control wires) either to the left or to the right, to store a zero or a one. The polarisations of the two layers are then either the same or opposite directions.Although the aluminum-oxide barrier is an electrical insulator, it is so thin that electrons are able to jump across it via a quantum-mechanical effect called tunnelling. It turns out that such tunnelling is easier when the two magnetic layers are polarised in the same direction than when they are polarised in opposite directions. So, by measuring the current that flows through the sandwich, it is possible to determine the alignment of the topmost layer, and hence whether it is storing a zero or a one.To build a full-scale memory chip based on MTJs is, however, no easy matter. According to Paulo Freitas, an expert on chip manufacturing at the Technical University of Lisbon, magnetic memory elements will have to become far smaller and more reliable than current prototypes if they are to compete with electronic memory. At the same time, they will have to be sensitive enough to respond when the appropriate wires in the control matrix are switched on, but not so sensitive that they respond when a neighbouring elements is changed. Despite these difficulties, the general consensus is that MTJs are the more promising ideas. Dr. Parkin says his group evaluated the GMR approach and decided not to pursue it, despite the fact that IBM pioneered GMR in hard disks. Dr. Prinz, however, contends that his plan will eventually offer higher storage densities and lower production costs.Not content with shaking up the multi-billion-dollar market for computer memory, some researchers have even more ambitious plans for magnetic computing. In a paper published last month in Science, Russell Cowburn and Mark Well and of Cambridge University outlined research that could form the basis of a magnetic microprocessor — a chip capable of manipulating (rather than merely storing) information magnetically. In place of conducting wires, a magnetic processor would have rows of magnetic dots, each of which could be polarised in one of two directions. Individual bits of information would travel down the rows as magnetic pulses, changing the orientation of the dots as they went. Dr. Cowbum and Dr. Welland have demonstrated how a logic gate (the basic element of a microprocessor) could work in such a scheme. In their experiment, they fed a signal in at one end of the chain of dots and used a second signal to control whether it propagated along the chain.It is, admittedly, a long way from a single logic gate to a full microprocessor, but this was true also when the transistor was first invented. Dr. Cowburn, who is now searching for backers to help commercialise the technology, says he believes it will be at least ten years before the first magnetic microprocessor is constructed. But other researchers in the field agree that such a chip, is the next logical step. Dr. Prinz says that once magnetic memory is sorted out “the target is to go after the logic circuits.” Whether all-magnetic computers will ever be able to compete with other contenders that are jostling to knock electronics off its perch — such as optical, biological and quantum computing — remains to be seen. Dr. Cowburn suggests that the future lies with hybrid machines that use different technologies. But computing with magnetism evidently has an attraction all its own.In developing magnetic memory chips to replace the electronic ones, two alternative research paths are being pursued. These are approaches based on:
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MCQ->Assertion (A): When an electron is revolving in its orbit and magnetic field is also present, the angular frequency of electron will be affected by the magnetic field.Reason (R): In the case of electron revolving in its orbit in the presence of magnetic field, the orbital magnetic dipole moment is not affected by the presence of magnetic field.

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MCQ-> Read the passage carefully and answer the questions given below it. Certain words/ phrases have been given in bold to help you locate them while answering some of the questions. Once upon a time, there lived a washerman in a village. He had a donkey by the name of Udhata. He used to carry loads of clothes to the river bank and back home everyday. The donkey was not satisfied with the food, that was given to him by his master to eat. So he wandered into the nearby fields stealthily and ate the crops growing there. Once, the donkey, while wandering around, happened to meet a fox. Soon, both of them became friends and began to wander together in search of delicious food. One night, the donkey and the fox were eating water-melons in a field. The water- melons were so tasty, that the donkey ate in a large quantity. Having eaten to his appetite, the donkey became so happy that he was compelled by an intense desire to sing. He told the fox that he was in such a good mood that he had to express his happiness in a melodious tone. ‘Don’t be a fool. If you sing, the people sleeping in and around this field will wake up and beat us black and blue with sticks,’ said the fox worriedly. `You are a dull fellow’, the donkey said hearing the words of fox. ‘Singing makes one happy and healthy. No matter what comes. I’ll definitely sing a song.” The fox became worried to see the donkey adamant to sing a song in the midst of the field, while the owner was still sleeping only a little distance away. Seeing his adamance, he said to the donkey, ‘Friend, wait a minute before you start first, let me jump over to the other side of the fence for my safety.’ Saying so the fox jumped over to the other side of the fence without losing a moment. The donkey began in his so-called melodious tone. Hearing, suddenly, a donkey braying in the field, the owner woke up from his sleep. He picked up his stick lying by his side and ran towards the donkey who was still braying happily. The owner of the field looked around and saw the loss caused by the donkey. He became very angry and beat him so ruthlessly that the donkey was physically incapacitated temporarily. He, somehow, managed to drag himself out of the field with great difficulty. The fox looked at the donkey and said in a sympathetic tone, T m sorry to see you in this pitiable condition. I had already warned you, but you didn’t listen to my advice.’ The donkey too realised his folly and hung his head in shame.Why did donkey want to sing ?
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