Answer
$(a)$ connect the ammeter in series with the element and just before it.
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$(b)$ connect the ammeter in series with the element and just after it.
Work Step by Step
An ammeter is a device for measuring current, it consists of a galvanometer and a shunt resistor in parallel. Ammeters are connected in series with the circuit element carrying the current to be measured and have very little resistance.
Hence, in order to make a correct measurement of current in a circuit element the ammeter should be attached in series just before or after the element.
