A free-of-charge, online 3D modeling program that runs in a web browser. One of its best features is to simulate electronic components and how they behave.

One popular free-of-charge, online 3D modeling program that fits your description is Tinkercad. Tinkercad is user-friendly and designed for individuals who want to create 3D models and simulations without needing extensive experience in modeling software.

A standout feature of Tinkercad is its electronics simulation capabilities. Users can design electronic circuits using virtual components like resistors, LEDs, and microcontrollers. The program allows users to see how these components behave in real-time through simulations, which is particularly useful for beginners learning about electronics or for educators teaching concepts of circuitry.

Additionally, Tinkercad offers a straightforward interface where users can drag and drop components, make connections via virtual wires, and test their designs. This makes it an excellent educational tool for classrooms and hobbyists alike. Overall, Tinkercad combines 3D modeling and electronics simulation effectively, providing a comprehensive platform for creative and educational purposes.