Cells in Series and Parallel — Definition

Definition

Imagine you have several small power sources, like AA batteries. How you connect them determines how much 'push' (voltage) they can give and how long they can sustain a 'flow' (current). This is precisely what we study when we talk about 'cells in series and parallel'.

Cells in Series: Think of a train. Each compartment is connected one after the other. Similarly, when cells are connected in series, the positive terminal of one cell is connected to the negative terminal of the next cell, and so on.

It's like stacking up the voltage. If each cell provides, say, 1.5 Volts, connecting two in series would give you 3 Volts, and four would give 6 Volts. The total voltage (or electromotive force, EMF) of the combination increases.

However, the internal resistance of each cell also adds up. Internal resistance is like a small 'friction' inside the battery that resists the flow of current. So, in series, both the total EMF and the total internal resistance increase.

This setup is useful when you need a higher voltage for your device, like in a TV remote or a flashlight.

Cells in Parallel: Now, imagine several identical water pipes all feeding into a single, larger pipe. This is similar to cells in parallel. All the positive terminals of the cells are connected together, and all the negative terminals are connected together.

For this connection to be most effective and to avoid internal current circulation (which wastes energy), it's crucial that all cells have nearly identical EMFs. When cells are connected in parallel, the total voltage across the combination remains the same as the voltage of a single cell (assuming they are identical).

However, the total current capacity increases, and the effective internal resistance of the combination decreases. This is because the current has multiple paths to flow through, effectively sharing the load.

This setup is commonly used when you need to supply a large amount of current or extend the operating time of a device, such as in car batteries or power banks, where multiple cells are connected in parallel to provide higher capacity without increasing the voltage.

In essence, series connections boost voltage, while parallel connections boost current capacity and reduce overall internal resistance (for identical cells). Understanding these fundamental connections is key to designing and analyzing electrical circuits that use multiple power sources, which is a very common scenario in electronics and everyday devices.