电子技术手册（英文版）

A passive electronic component is a circuit part that functions without an external power
requirement. The most common passive components are resistors, capacitors, and inductors.
Most of them have two leads. An axial-leaded component, as shown in Fig. 1-1, has leads
projecting from each end of the component body aligned with the long axis of the part, while
a radial-leaded component, as shown in Fig. 1-2, has parallel leads projecting at right angles
from its body. Axial leads must first be bent 90° to insert them into the holes of circuit
boards, while radial leads can typically be inserted directly into those holes without bending.
However, both axial- and radial-leaded parts can be inserted by automatic machines.