Question

why ammeter should bot be connected in parallel and voltmeter not in series

Answer 1

A voltmeter is used to measure the potential difference across two points in a circuit. Since, in parallel connection the voltage in the branches remains same, and also the resistance of the voltmeter is very high due to which a very small current flow through the voltmeter. So, it is connected in parallel to measure the voltage.

An ammeter is used to measure the current flowing through a component/circuit. Since, current remains same in series connection and also the resistance of an ammeter is very small due to which it doesn’t affect the current to be measured. So, an ammeter is connected in series to measure current.