Until the 1600’s, people who investigated problems related to our understanding of the natural world were called __?

Philosophers

Explanation:

Until the 1600's people who studied the natural world were called Philosophers.

Nowadays, we call them scientists.

Socrates, Aristotle, Democritus and other notable scholars of those days were all called Philosophers but they made important contribution that would help understand system of the natural world.

current and voltage can both be different in different parts of a circuit so it matters where you place the ammeter and voltmete