The correct answer is A. 1.8 V.
A lead-acid cell is a type of rechargeable battery that is commonly used in cars and other vehicles. It consists of two lead plates that are submerged in a sulfuric acid solution. When the battery is discharged, the lead plates react with the sulfuric acid to produce lead sulfate and water. This reaction releases electrons, which flow through an external circuit to power a device.
The lead sulfate that is produced during discharge can build up on the lead plates, which can reduce the capacity of the battery. If the battery is discharged too deeply, the lead sulfate can become so thick that it can bridge the gap between the lead plates, which can cause a short circuit. This can damage the battery and make it unusable.
To prevent this, it is important to never discharge a lead-acid cell beyond 1.8 V. This is the point at which the lead sulfate begins to form. If the battery is discharged below this point, it can be damaged.
Option B, 1.9 V, is incorrect because it is above the safe discharge point of 1.8 V. Option C, 2 V, is incorrect because it is also above the safe discharge point. Option D, 2.1 V, is incorrect because it is even higher than 2 V.
It is important to note that the safe discharge point of a lead-acid cell can vary depending on the type of battery and the manufacturer. It is always best to consult the manufacturer’s specifications for the specific battery you are using.