Question

why does an ammeter burns out when connected in parallel?

Answer 1

since the ammeter is a low impedance device, connecting it in parallel with the circuit will cause a short circuit, damaging the ammeter or the circuit

Answer 2

it happens bcoz ammeter has very low resistivity and therefore allows all the current to pass through it and is hence connected in series

but if u connect it in parallel then bcoz of its low resistivity it will burn