Magnetic field: Lines originating from the north pole and leading to the south pole of a magnet. This will also be generated when current flows through a wire. It should be in a circular pattern. The direction and magnitude of this will change according to the magnitude and direction of the current.
Right Hand Rule
Index finger: direction of magnetic fields
Thumb: direction of conductor
Middle finger: direction of current
Coils and Electromagnetic Induction
When a bar magnet moves within a coil, current flows in that coil which creates a magnetic field in order to oppose the change in magnetism. If the direction of movement of the bar magnet changes, the direction of the current in the wire also changes. This is the electromagnetic induction. The electricity that is generated during this process is induced by electromotive force. And, the current generated is induced current.
Coils and Inductance
If a coil is connected to a battery, current will flow through it and a magnetic field is generated. And, the coil becomes an electromagnet. At this time an induced electro-motive force is generated on the coil itself due to varying magnetic fields. This is Induction.
When the current to the coil is cut off, the magnetic field begins to disappear and an induced electromotive force is generated in the direction that obstructs the flow of current in the coil. This is counter electromotive force.