caption: The image shows a diagram of a magnetic field with a red circle in the center and a black background. The red circle is surrounded by text that reads "magnetic field". The diagram is composed of several concentric circles, each with a different color, and the text is written in a bold font. The colors of the circles range from light blue to dark blue, creating a gradient effect. The text is centered in the middle of the diagram, giving it a balanced and symmetrical look.