The system needs an ordinary friction-based brake to bring the train to a full stop. Explain why the magnetic brake is not very efficient when the train is moving slowly. The system needs an ordinary friction-based brake to bring the train to a full stop. Explain why the magnetic brake is not very efficient when the train is moving slowly. The slower the train is moving, the greater are the changes of the magnetic flux, thus the eddy currents become stronger. The slower the train is moving, the less are the changes of the magnetic flux, thus the eddy currents become weaker. The slower the train is moving, the less are the changes of the magnetic flux, thus the eddy currents become stronger. The slower the train is moving, the greater are the changes of the magnetic flux, thus the eddy currents become weaker.