The chemical effect of current is used in

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D.C. ammeter hour meter

Explanation: The chemical effect of electric current, based on Faraday's Laws of Electrolysis, is utilized in DC Ampere-hour meters (electrolytic meters). These devices measure the total quantity of electricity (charge) passed through a circuit over a period of time, where the mass of material deposited is proportional to the current-time integral.

Working Principle: The principle relies on Faraday's first law of electrolysis, which states that the mass $m$ of a substance liberated at an electrode is proportional to the quantity of electricity $Q$ passed through the electrolyte. Since $Q = \int I dt$, the amount of substance deposited corresponds directly to the total Ampere-hours consumed. The device consists of an electrolytic cell where current flow causes a measurable chemical change, such as the deposition of a metal or the release of a gas.

Key Formulas: $m = ZIt$ — mass liberated proportional to current $I$ and time $t$; $Q = \int I dt$ — total quantity of charge measured by the electrolytic meter

Key Points: Electrolytic meters are primarily used for DC measurements due to the unidirectional nature of ion flow.; The chemical effect of current occurs exclusively in electrolytes where ions move toward oppositely charged electrodes.; These meters were historically used for energy billing before the advent of motor-type induction meters.

Advantages: Simple construction without moving parts in basic designs; Independent of magnetic field interference; Integrates current over time naturally

Disadvantages: Requires periodic electrolyte replacement; Not suitable for AC measurements (ions oscillate instead of migrating); Slow response compared to electronic digital meters

Applications: Historical DC energy metering; Electroplating current monitoring; Battery charging capacity integration

Additional Info: Option B (DC Ammeter) usually operates on the Moving Coil (PMMC) principle, which uses the magnetic effect of current, not the chemical effect.. Option C (DC energy meter) is a broader term; however, specific chemical-based energy meters are classified as Ampere-hour meters.

Answer: A is correct — The DC Ampere-hour meter uses the chemical effect of current, governed by Faraday's laws, to integrate current over time via electrolytic deposition.

Exam Tip: Always distinguish between the three effects of electric current: Heating (I^2R), Magnetic (Electromagnetism/PMMC), and Chemical (Electrolysis). PMMC instruments use magnetic effects, while electrolytic cells use chemical effects.

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