Concept:A hot wire ammeter measures current by using the thermal energy produced in a wire when current flows through it.
Explanation:When electric current passes through a wire, it generates heat due to the heating effect of the current.
In a hot wire ammeter, this heat causes the wire to expand and move a pointer.
The amount of expansion is proportional to the current, so the pointer gives the current reading.
Moving iron ammeters and galvanometers operate using the magnetic effect of current, not the heating effect.
An electric heater uses the heating effect, but it is not a measuring instrument.
Answer:The correct option is B. hot wire ammeter.