88. Read the statements and select the correct alternative. Statement P: In a maglev train, there is no friction between the rail and the train. Statement Q: There is repulsion in like poles of an electromagnet. Statement R: Maglev train has the highest speed. ® P is the principle supporting Q and R is the effect of Q. ® Q is the principle supporting P and R is the effect of P. © R is the principle supporting P and Q is the effect of P. O P is the principle supporting R and Q is the effect of R.
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Answer:
Explanation:
maglev, also called magnetic levitation train or maglev train, a floating vehicle for land transportation that is supported by either electromagnetic attraction or repulsion. Maglevs were conceptualized during the early 1900s by American professor and inventor Robert Goddard and French-born American engineer Emile Bachelet and have been in commercial use since 1984, with several operating at present and extensive networks proposed for the future.
Maglevs incorporate a basic fact about magnetic forces—like magnetic poles repel each other, and opposite magnetic poles attract each other—to lift, propel, and guide a vehicle over a track (or guideway). Maglev propulsion and levitation may involve the use of superconducting materials, electromagnets, diamagnets, and rare-earth magnets.
Gotthard Base Tunnel
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railroad: Maglev
As an alternative to high-speed rail based on traditional flanged-wheel vehicles, the technology of magnetic levitation, or maglev,...
Electromagnetic suspension (EMS) and electrodynamic suspension (EDS)
Two types of maglevs are in service. Electromagnetic suspension (EMS) uses the attractive force between magnets present on the train’s sides and underside and on the guideway to levitate the train. A variation on EMS, called Transrapid, employs an electromagnet to lift the train off the guideway. The attraction from magnets present on the underside of the vehicle that wrap around the iron rails of the guideway keep the train about 1.3 cm (0.5 inch) above the guideway.
Electrodynamic suspension (EDS) systems are similar to EMS in several respects, but the magnets are used to repel the train from the guideway rather than attract them. These magnets are supercooled and superconducting and have the ability to conduct electricity for a short time after power has been cut. (In EMS systems a loss of power shuts down the electromagnets.) Also, unlike EMS, the charge of the magnetized coils of the guideway in EDS systems repels the charge of magnets on the undercarriage of the train so that it levitates higher (typically in the range of 1–10 cm [0.4–3.9 inches]) above the guideway. EDS trains are slow to lift off, so they have wheels that must be deployed below approximately 100 km (62 miles) per hour. Once levitated, however, the train is moved forward by propulsion provided by the guideway coils, which are constantly changing polarity owing to alternating electrical current that powers the system.
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Maglevs eliminate a key source of friction—that ond us. It’s...
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