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Quick launch roller coasters are designed to accelerate rapidly which allows the cars to reach maximum height. This contrasts with a typical chain-lift coaster which reaches the peak height slowly through the use of an inclined plane and pulley system. Modern quick launch roller coasters use several different technologies; hydraulics are the most common. Historically, however, the earliest quick launch roller coasters used a linear induction motor, a variant on a traditional electric motor.
The linear induction motor, used on so-called mag-launch coasters, is essentially an unrolled electric motor in which the commutator has been removed. The commutator is unnecessary because there is no need to reverse current directionality in a non-spherical motor. The rotor and stator are both present in a typical orientation, either flat or U-shaped. A diagram of a roller coaster with a flat linear motor with alternating areas of magnetic polarity is shown in Figure 1. To cause acceleration, half of the regions are inactivated.
Figure 1. Magnetic roller coaster track and cart
Force generated in most linear motors is proportional to both the current generated and the magnetic field such that F=ILXB where I is a proportionality coefficient, assumed to be one unless otherwise calculated. Interestingly, the object to be moved is often not in itself carrying a current initially. Rather, a current is induced according to Lenz’s law which acts to form its own magnetic field opposing the magnetic field of the stationary component. To create propulsion in this case, the electromagnetic regions are activated sequentially rather than simultaneously. Each region of the motor plate is supplied by a series of insulated coils around an iron core. The iron is exposed to the magnetic effects, but not the initial current.
Linear induction motors have fallen out of favor as sources of rapid acceleration, but are used commonly in other applications. Transit authorities in the US and overseas use them for mass transit, while theme parks use them for slow speed transit like monorails. In addition, linear induction motors continue to be used for rapid acceleration of small items like loom shuttles in industry and bullets in experimental weaponry.
To generate a magnetic field capable of accelerating the central car of the roller coaster, in what direction should the electric coils be oriented?
Vertically, so that the center of the coil directly faces the body to be moved
Horizontally, so that the center of the coil is parallel to the body to be moved
Longitudinally, so that the center of the coil is perpendicular to the body to be moved
None of the above, a straight wire should be used instead of a coil.
Can someone explain why that is the answer?
The linear induction motor, used on so-called mag-launch coasters, is essentially an unrolled electric motor in which the commutator has been removed. The commutator is unnecessary because there is no need to reverse current directionality in a non-spherical motor. The rotor and stator are both present in a typical orientation, either flat or U-shaped. A diagram of a roller coaster with a flat linear motor with alternating areas of magnetic polarity is shown in Figure 1. To cause acceleration, half of the regions are inactivated.
Figure 1. Magnetic roller coaster track and cart
Force generated in most linear motors is proportional to both the current generated and the magnetic field such that F=ILXB where I is a proportionality coefficient, assumed to be one unless otherwise calculated. Interestingly, the object to be moved is often not in itself carrying a current initially. Rather, a current is induced according to Lenz’s law which acts to form its own magnetic field opposing the magnetic field of the stationary component. To create propulsion in this case, the electromagnetic regions are activated sequentially rather than simultaneously. Each region of the motor plate is supplied by a series of insulated coils around an iron core. The iron is exposed to the magnetic effects, but not the initial current.
Linear induction motors have fallen out of favor as sources of rapid acceleration, but are used commonly in other applications. Transit authorities in the US and overseas use them for mass transit, while theme parks use them for slow speed transit like monorails. In addition, linear induction motors continue to be used for rapid acceleration of small items like loom shuttles in industry and bullets in experimental weaponry.
To generate a magnetic field capable of accelerating the central car of the roller coaster, in what direction should the electric coils be oriented?
Vertically, so that the center of the coil directly faces the body to be moved
Horizontally, so that the center of the coil is parallel to the body to be moved
Longitudinally, so that the center of the coil is perpendicular to the body to be moved
None of the above, a straight wire should be used instead of a coil.
Can someone explain why that is the answer?
