Question

? why is voltmeter connected in parallel and ammmeter in series?

Answer 1

Voltmeter is required to calculate the potential difference between two points. if it is connected in series then the potential diff between two consecutive points will be zero. So, it's useless.

Ammeter is used to calculate the current flowing in a branch. If it is connected in parallel, then the current will be divided between different branches and neither branch will get sufficient current so it is connected in series.