The diagram below shows passive components, resistors, capacitors and inductors, and also electrical components such as switches, relays, motors and lamps. Also shown are the symbols for wires that are not joined ( no physical electrical connection ) and wires that are joined ( a physical electrical connection ).

This next diagram depicts active components, the difference between active and passive is that active components require a power source to work, whereas passive components do not. The top symbols represent vacuum tube or thermionic devices. Although at one time, these were being replaced by the smaller transistor and integrated circuits, they are finding their way back into electronics for use in professional audio equipment and some radio receivers