Why is an ammeter connected in a series?

Why is a voltmeter connected in parallel with a circuit?

Obtain an expression for the equivalent resistance when n identical resistors each having resistance R are connected in series.

By mistake, a voltmeter is connected in series and an ammeter In parallel with a resistance in a circuit, What will happen to the instrument?

n-identical cells each of emf E and internal resistance r are connected in series. Find the expression for current in the circuit given below.

Obtain an expression for equivalent resistance of three conductors when they are connected in series.