JEE MAIN - Physics (2004 - No. 32)

Alternating current can not be measured by $$D.C.$$ ammeter because

Average value of current for complete cycle is zero

$$A.C.$$ Changes direction

$$A.C.$$ can not pass through $$D.C.$$ Ammeter

$$D.C.$$ Ammeter will get damaged.

$$D.C.$$ ammeter measure average current in $$AC$$ current, average current is zero for complete cycle. Hence reading will be zero.