Series and Parallel Circuits


  • Four (4) Wires
  • Batteries Block
  • 2 Lightbulb Blocks (or 1 Lightbulb Block and 1 Motor Block)
  • Any Switch Component Block

So far, each circuit we've made has had one pathway from the positive side back to the negative side of the Batteries Block. A circuit with all components in one pathway is called a series circuit. You may have discovered that we are limited to what we can do with a series circuit.

Build this circuit:

Describe the brightness of the lightbulbs. Are they as bright as when you have only one lightbulb in a circuit? Build a circuit with only one lightbulb to verify your observation. Why do you think the light is dimmer when you have two lightbulbs in the pathway? With just one set of batteries, how could you make a circuit so that each lightbulb glows brightly? Try to struggle with this for a long time before reading on.

Try to set up a parallel circuit, where each Lightbulb Block (or other HAPPEN Component Block) has its own pathway from the positive to the negative terminal of the Batteries Block. This can be done in multiple ways - explore and think about how many different ways you could do this.

How could you add a switch to your circuit to control only one light? How could you add a switch to your circuit to control both lights at once? Struggle with this for a long time. Continue to explore different ways switches can control lights in a parallel circuit.

Be careful that you don't make short circuits. Anytime a switch works in reverse in a simple circuit, where the lights turn off when the switch is closed, you have made a short circuit. This is not a good thing. A short circuit occurs when there is a pathway without a HAPPEN component from the positive to the negative terminals of the batteries. When you realize you have a short circuit, disconnect a wire from your batteries right away and inspect to figure out why you have a short circuit (remember: trace your paths slowly and carefully). Your Batteries Block has a resettable fuse that protects against short circuits, but it is important to learn to always avoid short circuits.

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