Induced current Experiment in the lab: A long wire is placed horizontally; a galvanometer in line allows to see the direction of the electrons in the wire. The tip of the needle goes in the same direction as the electrons. One end of this wire is close to a big ball and the other end of the wire touches the ground. Nearby, we place another horizontal wire connected to another ball and which also ends on the ground. An in-line galvanometer makes it possible to see the direction of the electrons in this wire also. We charge the big ball with electrons by friction. When the charge is large enough, a spark jumps from the big ball to the big horizontal wire. The electrons in the wire go to the ground, indicated by the arrow and the galvanometer. Then the flow of electrons stops. This happens in a fraction of a second.
Strange fact: a flow of electrons in the second wire is created when the flow in the big wire stops. The direction of the electrons is in the opposite direction. These electrons come from the small ball and go to the ground.
Question: What is the real cause of the 2nd flow of electrons called induced current? Consider the horizontal wire running north-south. When the spark jumps on the wire, billions of electrons are pushed into the wire and go to the ground. The speed of this displacement is almost c because it is caused by the electric ‘field’ caused by the spark. This field goes in all directions and the intensity decreases with the square of the distance. (The field is explained in another text).When this field reaches the north end of the wire, it causes a surplus of volts which causes a field that goes in all directions. The direction of the field acting on the north-south wire is only the part of that field going in a north-south direction. This pushes the electrons into the wire and they finally move towards the ground. Then the flow stops and the density of the field falls to zero. But in the lab, there are still fields caused by electrons from lab objects.
In summer, moist air tends to neutralize objects with less load or more load. In winter, if the air is dry, there are areas in the lab where the intensity of the field is different. When the field from north to south arrived, it affected the field already in the lab. Similar to a big bubble spreading, it has pushed on the field present in the lab. If we could measure the different directions of the field near the north-south wire, we would see that there is much more quantum going south.When the north-south field ceases, the lab field stabilizes and this causes a greater amount of quanta now going north. This instability now acts on the electrons of the second wire and pushes the electrons into the wire to the north. This causes the induced current of the second wire and then everything stops.
It is for this reason that an alternating current in a transformer is required to cause primary field changes that cause field changes at the secondary and thus an inverse induced current that is out of phase with the primary.