Here's a breakdown:

* Lines of Force: These are imaginary lines representing the direction and strength of a magnetic field.

* Conductor: A material that allows electric current to flow through it easily (like copper wire).

* Induced EMF: This is the voltage generated in a conductor due to the changing magnetic field.

The principle behind this is Faraday's Law of Electromagnetic Induction:

* Faraday's Law: It states that the magnitude of the induced EMF is proportional to the rate of change of the magnetic flux through the conductor.

* Magnetic flux: This is the measure of the amount of magnetic field passing through a given area.

Here's how it works:

1. When a conductor moves through a magnetic field (or a magnetic field changes around a stationary conductor), the magnetic flux through the conductor changes.

2. This change in magnetic flux induces an EMF in the conductor.

3. The induced EMF drives a current through the conductor, creating a flow of electrons.

Applications of this principle:

* Generators: These devices use mechanical energy to rotate a conductor in a magnetic field, inducing EMF and generating electricity.

* Transformers: These devices use changing magnetic fields to transfer electrical energy from one circuit to another.

* Electric motors: These use magnetic fields to create rotational motion, driven by the interaction of magnetic forces and induced currents.

In short, cutting lines of force with a conductor creates an electric potential difference (EMF), which is the basis for many essential electrical technologies.