It’s easy to see how the current flows through a circuit that has only one component, like one LED connected to the battery. If it’s a 3 Volt battery, then there’s 3 Volts across the LED also.

But what if there are two or three LEDs? How does the voltage look across each one? What if the LEDs are different sizes? Does it matter how you hook them up, meaning does one way make the LED last monger or glow brighter? Let’s take a look at the difference between series and parallel connections.

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You can have resistors in series, batteries in parallel, motors in series and parallel, and hundreds more different combinations! It all depends on what you want to do and how you want to do it.

For example, a 6V lantern battery is actually made up of four D-cell batteries connected in series. Each D-cell is 1.5V, and when you add four of them up, you get 6V. The older models of these used to have 24 AA batteries which were connected in series and parallel to make 6V. We’re going to learn how to decide whether to use a series or parallel circuit, depending on what we’re building and what we need the circuit to do.

Which bring up another point… what’s the difference between a D-cell and a AAA battery? They both are 1.5 volts. Why use one over the other? And 9V batteries are smaller and lighter than a D-cell but have  6 times the voltage… why wouldn’t yo use 9V for everything?

It has to do with current (the rate of charge flowing through the circuit). A D-cell has much more current than a AAA battery, and you’d use D-cells for things like motors. AAA are perfect for LEDs and other low-current devices that don’t need as much amps to get them going. In your circuit, you want to choose the best option that will still work voltage and amperage-wise, is the least expensive, and lasts long enough so you’re not changing batteries every few minutes.

Click here to go to your next lesson on Series Circuits.

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