What type of device converts DC electrical energy into mechanical energy?

A DC electric motor is the device specifically designed to convert direct current (DC) electrical energy into mechanical energy. In a DC motor, electrical energy from a power source is fed into the motor windings, creating a magnetic field. This interaction between the magnetic field and the current-carrying conductors generates a torque that causes the rotor to spin, thus producing mechanical motion.

This process of conversion relies on the principles of electromagnetism, where a current-carrying conductor in a magnetic field experiences a force. The efficiency and performance of a DC motor can be influenced by factors such as the strength of the magnetic field, the amount of current flowing through the motor, and the design of the motor itself.

In contrast, other devices listed serve different functions: an AC generator converts mechanical energy into alternating current (AC) electrical energy, an inverter transforms DC into AC power (not mechanical energy), and a transformer changes the voltage level of AC electrical energy without converting it to mechanical energy. Thus, in terms of converting DC electrical energy specifically into mechanical energy, the DC electric motor is the appropriate choice.