The teacher reversed the direction of the magnetic field. The teacher replaced the wire in its original position. The teacher moved the wire upwards in the same way as before. What was the deflection of the needle on the ammeter?

The direction of the induced current is determined by Fleming's Right-Hand Rule, which relates the direction of the Force/Motion, the magnetic Field, and the Current. - Initially, moving the wire up in the original field produced a current of +0.4 mA. - In the new setup, the direction of motion (upwards) is the same. - However, the direction of the magnetic field has been reversed (e.g., by swapping the N and S poles). If you reverse either the direction of motion or the direction of the magnetic field, the direction of the induced current will also be reversed. Since the magnitude of the motion and the field strength are the same, the size of the induced current will be the same, but in the opposite direction. Therefore, the needle will deflect to -0.4 mA.