Some superconducting maglev trains use the diamagnetism of superconductors to make the train body fl

The conductor rod AD and BC each cut the magnetic inductance line at the speed of the relative magnetic field (V VM), and the current direction generated in the loop is ABCDA, the electromotive force generated in the loop is E 2BL (V VM), and the current in the loop is: I 2BL (V VM) R, because the left and right sides of AD and BC are subjected to ampere force, then the ampere force F is combined with 2 BLI 4B2L2(V VM) R, according to the topic, the resistance of the metal frame when it reaches the maximum speed is balanced with the ampere force, then FF F is combined, the speed at which the magnetic field moves at a uniform speed to the right is obtained.

v＝(4b2l2vm＋ffr)/(4b2l2)<>

To stop the car, start with a few quantities above: B decreases, VM decreases.

;i=2e r solves i

e=bb(v0-v);i=2e r solves v0

3.Remove one of the magnetic fields; reduce the strength of the magnetic field; Reduces the speed of movement of the magnetic field.

3.change the direction of the magnetic field; change the direction of the current; Turn the coil upside down; ......

b conductor rod ad

and BC each with relative magnetic field velocity (vvm

Cutting the magnetic inductance line motion, the right-hand rule shows that the direction of the current generated in the loop is ABCDA, and the electromotive force generated in the circuit is E2BLV

VM, the current in the loop is I2BLV

VM R due to the left and right sides AD

and bc are both subjected to ampere, then the combined ampere force is f

Combine. 2×bli=4b

lvvm/r

According to the topic, when the metal frame reaches its maximum speed, the resistance is balanced with the ampere force, then the FFF is combined.

The velocity v(4b) of the magnetic field moving at a uniform speed to the right is obtained

lvmffr/4b

lb right.

(1) According to the right-hand rule, the direction of the induced current in the wireframe can be known as mnqpm or clockwise

2) When the motion is started, the speed of the metal frame relative to the magnetic field is v, and the induced electromotive force is e=2bbv

Induced current i e

r＝2bbv

r(3) when the acceleration of the metal frame a=0, the maximum velocity is vm, and the ampere force of the metal frame is f ampere = f, and f ampere = 2bib

i=2bb(v?vm)

r solution: vm v?rf4bb

4) To stop the metal frame, you can change the direction of the magnetic field, increase the resistance, cut off the power supply, etc

Answer: (1) The direction of the induced current in the metal frame at the illustrated position is mnqpm or clockwise;

2) The size of the induced current in the metal frame when the movement starts is 2bbvr;

3) The maximum speed that can be achieved by the metal frame is V-RF4BB

4) To stop the metal frame, you can change the direction of the magnetic field, increase the resistance, cut off the power supply, etc

Superconducting maglev train is the first application of superconducting technology that people may think of cautiously. More than 20 years ago, it was envisioned that superconducting technology would be used to make levitating trains and achieve high-speed rail transportation. Now China, Japan, Germany, Russia, the United Kingdom, France and other countries have successfully manufactured the fastest means of transportation on land——— superconducting suspension train, this kind of train is suspended on the superconducting "magnetic pad" roadbed, the speed is as high as 400km-500km, such as from Beijing to Shanghai only more than 3 hours.

Electric vehicles that have been put into service consist of a battery pack and a filial electric motor. Due to the limited storage capacity of the battery, such cars have a shorter trip. The use of high-temperature superconductors can greatly reduce the power loss of the battery, increase the storage capacity, and increase the power supply capacity.

In this way, electric vehicles will likely become popular in the world, which will undoubtedly be very beneficial to reducing air pollution and simplifying the structure of automobiles.

c Due to the interaction between magnetic fields, the height of the train is 100 mm, and the increased gravitational potential energy is δep = mgh = 20 103 10 100 10-3 J = J, and the correct option is c

Nitrogen is to keep the superconductor at a low temperature, and the superconductor currently has no room temperature, so it is a low temperature

2) 44s (can be seen as only one ball in imitation of the oak).

3) c a(-60) b(30) c(-80) (can be seen as a ball, each ballast moves to the left in a 36s distance of the ball).

(1) When the train is stationary, the current is maximum, and the maximum electromagnetic driving force on the train is set to fm, and the induced electromotive force generated in the wire frame is at this time.

e1=2nblv0

Current in the wireframe i1=er

The entire wireframe is subjected to ampere force fm

The resistance of the 2NBI1L train is FM F

m＝4nbl

vr(2) When the train moves at a constant velocity v, the speed of the two magnetic fields moving horizontally to the right is v, and the induced electromotive force e=2nbl(v) in the metal frame'-v）

Induced current I 2nbl (V?) in the metal framev)

r, and because f=2nbil=f

Find v v+fr4nb

lWhen the train moves at a constant speed, the thermal power in the metal frame is p1=i2rThe power to overcome the resistance is p2

fv so the total energy that the outside world needs to provide per unit time is .

e=i2r+fv=fv+fr4n

BL(3) According to the analysis of the topic, in order to realize the continuous linear motion of the train with uniform acceleration in the horizontal direction, its acceleration must be the same as the acceleration of the linear motion of the two magnetic fields from stationary to achieve uniform acceleration, and let the acceleration be a, then t1

Moment electromotive force in a metal coil.

e=2nbl（at1-v1

Induced current I 2nbl(at) in the metal frame

VR is also because of the ampere force f 2nbil 4nbl

at?VR So for trains, Newton's second law yields 4NBL

at?vr?f＝ma

Solve a fr+4nbl

v4nblt?mr

Let the time from the movement of the magnetic field to the start of the train be t0, then the electromotive force in the metal coil at t0 is e0 at the time t0

2nblat0

Induced current i in the metal frame

2nblat

r, because of the ampere force f

2nbil＝4nbl

ATR so for trains, by Newton's second law, gets 4nbl

ATR f gives T fr4n

bla＝fr(4nbl

t?mr)4nb

l(fr+4nblv