JAMB - Physics (1988 - No. 32)
Which of the following ammeters may be used to measure alternating currents? i. moving-coil ammeter ii. moving-iron ammeter iii. hot-wire ammeter
i and ii only
ii and iii only
i and iii only
i, ii, and iii
Vysvetlenie
Moving-coil ammeter: Primarily used for direct current (DC) only, as it relies on a constant magnetic field and does not accurately respond to AC.
Moving-iron ammeter: Suitable for measuring both AC and DC currents. It operates based on the magnetic effect of the current, making it effective for AC.
Hot-wire ammeter: Specifically designed for measuring AC currents. It utilizes the heating effect of the current and provides accurate readings for AC.