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Voltage: Parallel and Series Circuits (2019)
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1. Introduction: LED Sign -
2. Failed Series Circuit
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Check Your Understanding: Failed Series Circuit -
Mini-Project: Voltage Investigation
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3. Parallel Circuits
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Upload a photo of a parallel circuit used to power multiple independent loads. -
Mini-Project - Shared Voltage Nodes
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Check Your Understanding: Shared Voltage Nodes
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Wire Coloring
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Check Your Understanding: Parallel Circuits
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4. Power Panels - Managing Parallel Circuits
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Mini-Project: Mounting to the Terminal Block
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Mini-Project - Terminal Block with Jumper
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Check Your Understanding: Power Panels
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Unit Project: LED Sign
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Upload Photo: LED Sign
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Upload Block Diagram: LED Sign
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Series Circuit
Watch It Fail: Two-in-a-row
Important: The first circuit in this activity will not work as you might expect. This is intentional! Keep going to see why. Your sign needs more than one LED, so begin by building the circuit below with two LEDs in it.
Circuit with two LEDs
Explanation Voltage and Series Circuits
To get through the circuit, electricity needs to flow through both LEDs.
However, there is not enough electrical "push" in this system to get through both of them. This electrical "push" potential is called voltage.
The coin cell battery in your system provides 3.3 volts of Voltage.
It takes around 3 volts to "push" electrons through each LED. The LED harvests some of that passing electrical energy to create light, and leaves a lower remaining voltage on the other side -- 3 volts lower.
Voltage Illustration
When there is only one LED, there is enough [3.3 vs. 3] voltage to light the LED. The remaining .3 volts turn into heat inside the battery, which is not great, but not dangerous in this particular case.
When you set up the circuit with two LEDs in a row, you're asking the electricity to pass through both LEDs...
...and each of them needs 3 volts of electrical "push" to get through it.
That means one LED will take its 3 volts, then the other LED will need 3 more -- 6 in total. So if there aren't at least 6 volts of "push" available, electricity doesn't make it through the circuit.
And as we know from earlier, circuits only work when there is a constant flow of electricity. That means if there are less than 6 volts available, the whole circuit will fail.
Your circuit has 3.3 volts of potential "push" coming from the coin cell battery. That's not enough to get through two LEDs that each want to use up 3 volts (6 in total). Since there's not enough push to get all the way through, electricity doesn't flow at all, and neither light turns on.
This kind of circuit is called a series circuit, because electricity traveling through it has to go through a series of components one after another.