It is difficult to go through a day without seeing something powered by a battery, including our cars and wristwatches. Two types of batteries are quite common in the consumer market: the AA battery and the C battery. Both batteries provide the same voltage although the two types are often used in quite different applications.
The battery types include dry-cell, alkaline electrolyte batteries. An "electrolyte", according to The American Heritage Dictionary of the English Language, Fourth Edition, is "A chemical compound that ionizes when dissolved or molten to produce an electrically conductive medium." The electrolyte, in this case, is an alkaline compound that allows the battery to maintain a 1.5 volt difference between the positive electrode and the negative electrode. "Dry-cell" indicates that the electrolyte used is not a liquid, but rather a "dry", non-liquid, material.
AA batteries--also known as LR6 batteries--are used in many portable, low-current electronic devices, such as personal radios, small flashlights, and MP3 players. Due to their small size (0.57 in. diameter x 1.99 in long) and light weight (0.75 oz), AA batteries are used in applications where excess weight or size is unwanted.
However, AA batteries have a smaller capacity for work over a given time than larger batteries. An Energizer Ultra Plus AA battery, for example, will be able to power a device at 500 milliamps (mA) for three hours. By way of comparison, an Energizer Ultra Plus D battery, which is larger in size than AA and C batteries, is capable of powering a device at 500 mA for 24 hours.
C batteries--also known as LR14 batteries--are used in devices that have higher electrical current demands than AA batteries can support. Some typical applications for C batteries are larger flashlights, remote-controlled toys, and larger radios.
C batteries have a larger capacity for work over a given time than their AA counterparts. For example, an Energizer Ultra Plus C battery will be able to power a device at 500 milliamps (mA) for eight hours.
Due to their larger size (1.34 in diameter x 2.42 in long) and weight (4.5 oz), C batteries are not practical for use where small size or light weight is needed.
Although AA batteries and C batteries differ greatly in size, both types of batteries have a nominal voltage of 1.5 volts. The three major differences between the types of batteries are size, weight, and capacity. Depending upon the situation, or the specific needs of the device or electrical circuit to be powered, AA and C batteries are interchangeable to a large degree.
For example, in a situation where a low-power, low-current electrical circuit is to be powered for a short period of time--such as a low-power circuit in a science experiment--either battery would be appropriate.
If size, weight, or capacity--or some combination thereof--is a factor in which battery to use, it would be best to consider which battery would work better for the device or electrical circuit the battery will be used.