Question

what is an example of a series circuit?
a vacuum
a tv
a string of christmas lights
a lamp

Explanation:

A series circuit is a circuit in which components are connected end - to - end, so that the current flows through each component in turn. A string of Christmas lights is often a series circuit. In a vacuum, there is no circuit as it is an empty space. A TV and a lamp usually have more complex circuits (like parallel or combination circuits) rather than simple series circuits for their normal operation.

Answer:

a string of Christmas lights