The question asks to identify the physical quantity measured by the unit Ampere-hour (Ah).

Ampere-Hour Unit Explained

The Ampere-hour is a unit commonly used to describe the capacity of batteries. It represents the amount of electric charge transferred by a steady current of one ampere flowing for one hour.

Mathematically, it can be expressed as:

Where:

• Current is measured in Amperes (A).
• Time is measured in hours (h).

Since electric current is defined as the rate of flow of electric charge (charge per unit time), multiplying current by time gives the total quantity of charge that has flowed.

Therefore, the Ampere-hour directly measures the quantity of electricity, also known as electric charge.

Evaluating Other Options

• Strength of current: The strength or magnitude of electric current is measured in Amperes (A), not Ampere-hours.
• Power: Electric power is the rate at which energy is transferred or converted. It is measured in Watts (W). Power ($P$) is calculated as Voltage ($V$) times Current ($I$), so $P = V \times I$. An Ampere-hour does not directly represent power.
• Energy: Electrical energy is the capacity to do work. It is measured in Joules (J) or Watt-hours (Wh). Energy ($E$) is calculated as Power ($P$) multiplied by Time ($t$), so $E = P \times t = V \times I \times t$. While Ampere-hours are related to energy (Energy = Voltage $\times$ Ampere-hour), an Ampere-hour by itself is a measure of charge, not energy.

Conclusion on Ampere-Hour

The unit Ampere-hour (Ah) is fundamentally a unit of electric charge, representing the total amount of charge passed.