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Tiếng Anh Lớp 8
ViOlympic Tiếng Anh Lớp 8
Đề Thi ViOlympic Tiếng Anh Lớp 8 Vòng 6
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Effects of Electromagnetic Fields
Students made the device shown in the experimental setup below for testing the effects of different electromagnetic fields on substances. The testing device has three batteries, three coils of insulated copper wire, one iron rod, three adjustable selector switches, and one on/off switch with a power indicator light.
Six metal weights are available for the tests; each weight has the same volume and mass. The strength of the electromagnet is measured by counting the number of metal weights that can be suspended from the rod like a chain. A description of the functions of the device’s switches is below.
Which sequence correctly shows the energy conversions that allow the testing device to attract a metal weight with magnetic properties?
battery (chemical to heat) → wire coil (heat to magnetic) → metal weight (magnetic to frictional)
battery (chemical to electrical) → wire coil (electrical to magnetic) → metal weight (magnetic to mechanical)
battery (electrical to magnetic) → wire coil (magnetic to heat) → metal weight (heat to mechanical)
battery (electrical to mechanical) → wire coil (mechanical to magnetic) → metal weight (magnetic to gravitational)
Students attempted to use the device and the weights in an investigation. None of the metal weights were attracted to the electromagnet when they were placed near it. The students made sure that the power indicator light was on, then they tried every switch combination.
Which system modification and test are necessary to solve the design flaw in the experimental setup?
Use copper metal weights and test the batteries.
Use a copper rod and test the batteries.
Use smaller metal weights and test the original weights and the smaller weights with a bar magnet.
Use a larger iron rod and test the original metal weights with a bar magnet.
Which statement correctly describes the forces acting on the metal weights when the system design prevented them from being attracted to the electromagnet?
The balanced magnetic and gravitational forces were insufficient to overcome the inertia of the metal weight.
The balanced frictional and gravitational forces were insufficient to overcome the momentum of the metal weight.
The unbalanced frictional and gravitational forces were insufficient to overcome the inertia of the metal weight.
The unbalanced magnetic and gravitational forces were insufficient to overcome the momentum of the metal weight.
The power switch is on. Which procedure will best determine the type of circuit that makes an electromagnet?
Set switch 1 to S. → Change switches 2 and 3 to every combination. → Observe the motion of the metal weights.
Set switch 1 to P. → Change switches 2 and 3 to every combination. → Observe the motion of the metal weights.
Set switch 2 to a constant setting. → Change switches 1 and 3 to every combination. → Observe the motion of the metal weights.
Set switches 2 and 3 to constant settings. → Change switch 1 from P to S. → Observe the motion of the metal weights.
The diagram above shows some positions in the path of a pendulum swinging from a fixed point called a fulcrum.
The pendulum is raised to the start position and released.
At which two numbered positions is the potential energy of the pendulum most likely the same?
position 1 and position 3
position 1 and position 4
position 2 and position 3
position 2 and position 4
The map above shows some of the major tectonic plates on Earth.
What process is forming high nonvolcanic mountains at location 1 on the map?
One tectonic plate is splitting apart into two plates.
Two tectonic plates are colliding and pushing together.
One tectonic plate is sliding past another tectonic plate.
Two tectonic plates are colliding and one is sliding under the other.
A line of volcanoes occurs along the western coast of South America, near location 4.
Based on the information about plate movement on the map above, which process explains the formation of these volcanoes?
subducting of one plate under the other causing melting of the lower plate
sliding of one plate sideways past another resulting in friction and melting
melting of crust because of plate movement over a “hot spot”
rifting of a plate with lava filling in the resulting valley
The reproductive success of an organism depends in part on the ability of the organism to survive.
How does the physical appearance of these organisms help them survive?
Their physical appearance helps them find a habitat.
Their physical appearance helps them resist parasites.
Their physical appearance helps them avoid predators.
Their physical appearance helps them defend a territory.
Which of the following diagrams best shows the relative positions of Earth, the Moon, and the Sun during a lunar eclipse?
Monte Bolca is located high in the mountains of northern Italy. This site is one of the world’s largest deposits of coral reef fish fossils. There are fossils of more than 160 fish species dating back 49 million years.
These fossils provide evidence of the environment in which the coral fish lived and died.
Which statement is consistent with the evidence above and explains how ancient coral reef fossils can be found high in the mountains far from any sea?
A huge tidal wave pushed marine life up into the mountains.
Prehistoric man carried fish into the mountains from the sea.
Fish were thrown into the mountains by a tremendous volcanic explosion.
Land that was uplifted to form the mountains was once covered by the sea.
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Từ Vựng Tiếng Anh Lớp 8
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