What is the operational principle of an electric motor?

The operational principle of an electric motor is rooted in the interaction between electric current and magnetic fields, which is harnessed to create motion. In essence, an electric motor converts electrical energy into mechanical energy through electromagnetic interactions. When electrical current flows through coils of wire within a magnetic field, it generates a force according to the Lorentz force principle, causing the motor's rotor to turn. This conversion is essential for the functioning of any electric motor, as it allows machinery and devices to perform work.

The other options describe processes that are not applicable to electric motors. For instance, transforming mechanical energy into electrical energy pertains to generators, while converting thermal energy would relate more to thermoelectric devices. Additionally, while many electric motors can operate on battery power, they can also be powered by other sources, such as AC mains electricity, so stating that they operate solely on battery power is too limiting. Therefore, the correct answer accurately captures the fundamental working concept of how electric motors operate.