What is component 1 in figure T-1?

In standard electrical schematic diagrams, a resistor is universally represented by a jagged or zigzag line. This symbol visually depicts the concept of resisting or impeding the flow of electrical current, acting like a rough path for the electrons. Other components have distinctly different shapes. For example, inductors are drawn as a series of rounded loops or coils, while capacitors are drawn as parallel lines. Familiarizing yourself with the sharp zigzag shape is the easiest way to instantly identify a basic fixed resistor on an exam figure.