Question

Why ordinary ammeter used for dc cannot be used for ac?

Answer 1

Answer: Alternating current changes in magnitude and direction and the mean value of ac over a complete cycle is zero. Therefore moving coil ammeter will always read zero when connected in an ac circuit of any frequency.

Answer 2

✔Generally ordinary ammeter consists of PMMC (Permanent ... moving coil ) instruments which can measure dc values only. For ac values we use digital instruments.