Question

Suppose the ammeter or the voltmeter that you are using in the circuit do not have positive and negative terminal markings,how will you use such an ammeter or voltmeter in the circuit

Answer 1

We will use typical battery to determine this.
Connect them with wire and the battery, if their reading are positive then we have connected them correctly and if their reading in negative then we have connect them in opposite polarity.

we can also note the deflection in voltmeter or ammeter, one after other by changing the polarity.