Home
登錄
註冊
How do Maglev trains work? - Ning Zhao - Video học tiếng Anh
聽力練習
聽力練習
/
Video
/
TED-Ed
/
How do Maglev trains work? - Ning Zhao
How do Maglev trains work? - Ning Zhao
選擇學習模式:
查看字幕
選詞
重寫單字
字幕 (156)
0:00
[music]
0:05
[music]
0:06
>> To coincide with the 1964 Tokyo
0:09
Olympics, [music] Japan launched the
0:12
world's first high-speed train, the
0:15
Shinkansen, [music]
0:16
capable of running at 210 km/h.
0:21
This groundbreaking bullet train
0:23
inspired countries [music] around the
0:25
world to invest in high-speed rail.
0:29
Today, these trains regularly [music]
0:31
travel at over 300 km/h,
0:35
on par with the takeoff speed of a
0:38
commercial [music] airplane.
0:39
But, could these trains go even faster,
0:43
whisking passengers [music] to their
0:44
destinations quicker than the smoothest
0:47
flight?
0:48
To answer this, [music] it helps to
0:50
understand how these trains reach their
0:52
already impressive speeds. There are
0:55
[music] three main factors that separate
0:58
bullet trains from traditional low-speed
1:01
trains:
1:02
engines, aerodynamics, and
1:05
infrastructure. [music]
1:08
Most traditional trains are powered
1:11
[music] by combustion engines,
1:14
which combust fuel, typically diesel, to
1:17
turn an electric generator. [music]
1:19
This electricity is then used to power
1:22
motors that turn the train's wheels.
1:25
High-speed trains, [music]
1:26
on the other hand, use electric engines
1:29
to power their motors. This process is
1:32
more energy efficient [music] than
1:33
combustion, and allows train operators
1:37
to reach top speeds more quickly.
1:40
Next up is aerodynamics.
1:43
While low- and [music] high-speed trains
1:45
use the same steel wheels to minimize
1:48
friction with the track, bullet trains
1:51
are also [music] designed with
1:52
aerodynamic bodies that slice through
1:55
air with minimal [music] resistance.
1:58
Engineers could use these slicker
2:00
designs on traditional train cars.
2:02
[music]
2:03
But while upgrading to electric engines
2:05
would make low-speed trains more
2:07
efficient, they wouldn't [music] get
2:09
much benefit from these aerodynamic
2:11
designs because of the third factor,
2:14
infrastructure.
2:16
Traditional train tracks were built to
2:18
meet people [music] where they lived,
2:20
ensuring stations were accessible to any
2:23
potential passengers.
2:25
But to prevent derailments in these
2:27
highly populated areas, trains need
2:30
[music] to frequently decelerate to
2:33
safely hit turns and crossroads.
2:36
High-speed rails, on the other hand,
2:38
were built to prioritize speed. They run
2:41
on long, straight [music] lines that
2:43
avoid road crossings, sharp curves, and
2:46
high-traffic [music] areas.
2:49
These three differences allow high-speed
2:52
trains [music]
2:52
to reach top speeds over double their
2:55
traditional counterparts. And since
2:58
their infrastructure allows them to
3:00
travel longer distances [music] between
3:02
stops, they spend more time cruising
3:05
near top speed, often traveling [music]
3:08
up to three times the average speed of
3:11
traditional trains.
3:13
But new technology is emerging [music]
3:15
to make even faster trains.
3:19
To eliminate friction between rails and
3:21
wheels, engineers have developed new
3:24
magnetic levitation, or maglev, trains.
3:28
There are two major approaches here.
3:30
In electromagnetic suspension,
3:33
magnetized arms wrap under [music] the
3:35
track and pull the train up. Meanwhile,
3:39
in electrodynamic suspension, coils
3:42
embedded in the track [music] create a
3:44
pattern of alternating magnetic fields
3:47
that interact with magnets on the train
3:49
[music]
3:50
to float the vehicle a few centimeters
3:53
in the air.
3:54
To change speed, [music] train operators
3:57
alternate the direction of the train's
3:59
magnetic field, attracting the front of
4:02
the train to the next coil to speed up,
4:05
or reversing the field's [music] phase
4:07
to brake.
4:08
Given enough runway, these trains can
4:11
reach speeds from 430 to a theoretical
4:15
600 km/h,
4:18
allowing them to make the over 4,400
4:21
km trip from New York City to Los
4:24
Angeles in as little as 7 hours. [music]
4:27
So, why haven't we built Maglev trains
4:31
or even high-speed trains everywhere?
4:33
[music]
4:35
First, these trains require lots of
4:38
energy, most of which is needed [music]
4:40
to overcome air resistance. In fact, at
4:44
300 km/h, [music]
4:46
this task accounts for over 80% of
4:49
train's energy consumption.
4:52
Engineers [music] are researching ways
4:54
to reduce air resistance, such as
4:56
putting Maglevs in near vacuum
4:59
environments.
5:00
But, building a vacuum-sealed tunnel
5:03
across an entire country would be an
5:05
infrastructure [music]
5:06
project of science-fictional
5:09
proportions.
5:10
Besides, it's hard enough to build
5:12
regular high-speed rails. To go fast,
5:15
[music]
5:15
trains need long, straight tracks with
5:18
wide curves, which are very difficult to
5:21
build in mountains, cities, or [music]
5:24
densely populated areas.
5:26
Building such routes is costly,
5:29
politically sensitive, and often [music]
5:31
physically impossible.
5:34
Despite these hurdles, Japan and China
5:36
[music] are expanding their existing
5:38
high-speed and Maglev rails,
5:41
>> [music]
5:41
>> and several projects currently in
5:43
development might finally bring
5:45
high-speed rail to the US.
5:49
But, we'll need to carefully consider
5:51
our trains' top speeds alongside cost,
5:54
energy use, and safety to keep the
5:57
future of train travel on the right
5:59
track.
6:00
>> [music]
6:02
>> And that future could include you.
6:04
Brilliant can help you master the
6:06
fundamentals of math and programming
6:09
with a visual interactive tutor that
6:11
asks guiding questions, draws diagrams,
6:14
and adapts in real time to your learning
6:17
needs. Visit brilliant.org/ted-ed
6:20
to get started with Brilliant's tutor
6:22
for free and 20% off an annual premium
6:25
subscription.
