Question

resistance of ammeter should be negligible give reason

Answer 1

ammeter is connected in series with the circuit so the total current should flow through ammeter to measure it hence the ammeter should have negligible resistance. the ideal ammeter should have zero resistance

Answer 2

An ideal ammeter should have zero or negligible resistance so as to allow all current to pass through to get the accurate readings.
this is because the ammeter is connected in series to the circuit.