这个地球磁场的问题themetalwingofanairplaneactslikea"wire"flyingthroughtheEarth'smagneticfield.Avoltageisinducedbetweenthewingtipsandacurrentflowsalongthewing,butonlyforashorttime.Whydoesthecurrentstopev

Question

这个地球磁场的问题
the metal wing of an airplane acts like a "wire" flying through the Earth's magnetic field.A voltage is induced between the wing tips and a current flows along the wing,but only for a short time.Why does the current stop even though the airplane keeps flying through the Earth's field?(英语回答,）

Answer 1

变化的磁场才引起电流,或者说导体对磁场有相对运动才产生电流.
严格说,这段英文说的并不严格成立,是个大约中学水平的近似说法.
a specific case of a conductor moving relative to magnetic field,the magnetic field produced by the current due to the induced EMF in the conductor interacts with the external magnetic field that initially induced the EMF,and thereby produces a net force on the conductor opposing its movements across the magnetic field.
To generate current there has to be relative motion between the conductor (loop) and the magnet.They can both be moving,or just one can be moving,but if neither is moving,there is no current generated.Switching the circuit from one loop to the other when neither is moving,is pointless.