What is the purpose of an ampere-hour (Ah) rating in batteries?

The ampere-hour (Ah) rating of a battery serves to provide a measure of the battery's capacity to deliver a certain amount of current over a specified duration. This rating is crucial for understanding how long a battery can supply power to an electrical load before being depleted. For instance, if a battery has a rating of 10 Ah, it can theoretically deliver 10 amperes of current for one hour, or 5 amperes for two hours, etc. This capacity rating helps users to determine whether the battery is suitable for their specific application, ensuring that the power supply will last long enough to meet operational needs.

The other options, while related to aspects of batteries, do not accurately define the purpose of the ampere-hour rating. For example, the weight of the battery is not indicated by the Ah rating, nor does this rating measure voltage. Similarly, while efficiency is critical for chargers, it is not directly measured by the ampere-hour rating of a battery. Understanding the Ah rating thus allows users to make informed decisions about battery usage and suitability for various applications.