Question

AB AB B 8 In Out AB 8 nduoed Out In 8. To the right are 4 scenarios. Explain how each work with regard to changing magnetic fields (flux) and induced current direction. Make sure to use RHR2, The red parts refer to induced current.

Answer 1

Concept to be used: We know that the coil will work as an inductor and the nature of the inductor is that it will try to make the net flux constant irrespective of the external changes.

1. In first figure: We have a north pole which is moving toward the coil. We know that goes away from the north pole. So when the north pole is moving close to the coil then the net flux density (field line per unit area) in the coil will increase. But as the concept says the inductor tries to make it constant. For making the net flux density constant a circulating current will flow in the coil which will generate field lines to oppose the external flux. Using right hand thumb rule if the direction of current is in the direction of fingers then the field lines will be in the direction of thumb. Similarly the voltage generated can be calculated from the direction of current flowing.

2. In second figure: The north pole is moving away from the coil which implies decreasing magnetic fields in the coil so the induced current will flow in such a fashion so that it support the decreasing field lines.

Similarly using the same logic we can explain the all cases.

The induced current will always try to make the field line constant with respect to the external changes. If the field lines decreases it will try to increase it.