Class 10 Physics Magnetic Effects of Electric Current
As the current in the primary coil changes, the magnetic field associated with changes.
Then the magnetic field associated with the secondary coil also changes. And this causes the current
This process by which a changing magnetic filed in conductor induces a current in another conductor is called electromagnetic induction.
The direction of the current is given by Flemings Right Hand Rule : Stretch the thumb, forefinger and middle finger of your right hand such that they are mutually perpendicular to each other (as shown in the figure). If the thumb points in the direction of motion of the conductor, the forefinger points in the direction of the magnetic field and then the middle finger points in the direction of the induced current