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Children often learn better when they’re having fun. That’s why we created Squishy Circuits — to teach science, technology, and engineering through play. We recently put out the call to educators and asked them about developing projects and challenging students with Squishy Circuits. Keep reading to find out what some students in Washington state created — and learned.

Squishy Circuits uses batteries to power circuits. When you flip the battery holder’s switch, electrons flow from the batteries and power the LEDs, motors, or buzzers. In our daily lives, we’re used to having instant access to electricity in our homes.  It turns on our lights, heats our food, keeps our electronics running, and so much more!

So, where is the power coming from to power all of these devices? There surely isn’t a battery behind every outlet that we plug in to, right?

The answer is called the electrical or power grid. The grid works much like our road systems or the internet - electricity goes through a series of transformers, substations, cables, and more on its journey from the plant to your home. It’s not just a straight connection. A lot of organization and engineering has been put into the grid design to make sure everyone can have electricity. 

The grid begins with generation, or the act of creating electricity. Currently, most power grids begin with generation at a power plant. Fossil fuels or coal are burned and energy is generated by spinning a generator. Electricity can also be generated by solar panels, wind turbines, nuclear power, and more! The future is quickly adapting to our changing climate and moving away from burning fossil fuels and centralized power plants. 

Next, the generated electricity is converted to a higher voltage using step-up transformers. This step-up makes it more efficient to transfer over long distances. This high-voltage electricity is then sent through large power lines to substations.

Substations act as the middle link between your home and the power plant. They figure out where the power needs to go and when to send it. When there is demand, such as when you turn on the lights, sensors alert the substation and the substation sends electricity along cables that are held up by power poles or are buried underground to your home.

Before it can be used, the power must be reduced back down to a lower voltage. Have you ever seen those white canisters on the sides of power poles? These are called step-down transformers. They take the high-voltage power and convert it to a lower voltage before it arrives in your home.

Once the power gets delivered to your house, even then the power’s journey is not finished! Each house has an intricate set of wiring directing the power where it needs to go. The power from the step-down transformer gets sent to a fuse box which splits the electricity to different parts of your home and adds safety fuses which turn off the power in case of a fault. Wires in the wall connect each outlet, switch, light, and appliance back to the fuse box allowing us to use the electricity!

The next time you plug something into the wall or turn on the lights, think about the millions of electrons that have been zipping for many miles through wires, transformers, cables, and more! The grid is truly one of our modern marvels.

Buzzers add noise to our Squishy Circuits. But you’ll notice that there are two types – a mechanical buzzer and a piezoelectric buzzer. What’s the difference? Not just the shape of the case! The difference is how the buzzers create noise. If you compare the noises they create side-by-side, the mechanical buzzer creates a low pitch buzz, meanwhile the piezoelectric buzzer creates a high pitch beep. 

Mechanical buzzers create their noise by moving a metal tab (or armature) up and down using an electromagnet. When the electromagnet turns on, it attracts the armature pulling it down. When the electromagnet turns off, the armature springs back up. This happens thousands of times a second and creates vibration which in turn creates the ‘buzzing’ noise. You’ll notice if you push the buzzer against a ridged surface, it will be louder because it has a surface to resonate the vibrations.

Piezoelectric buzzers do not have a metal armature, but instead rely on a piezoelectric element. Piezoelectric is derived from the Greek word ‘piezo’ which means pressure or push. As the name implies, a piezoelectric element will create a small amount of electricity when it is pushed or flexed. Conversely, if you apply a voltage across a piezoelectric element, it will slightly flex. Piezoelectric buzzers rely on this process to create vibrations. The buzzer applies a voltage across the piezoelectric element thousands of times per second which flexes the piezoelectric element to create noise.

The pitch generated from a buzzer is called its frequency and is measured in hertz. A frequency of 1 hertz means that there is 1 cycle (vibration) per second. A frequency of 10 hertz means that there are 10 cycles per second. And so on…

We tested 5 of each type of buzzer with a frequency analyzer app and found that:

• The mechanical buzzers have a frequency of approximately 2600 hertz meaning that the metal armature is moving up and down 2600 times per second. Since the mechanical buzzers rely on the metal armature, there is more variability in their individual frequencies.
   
• The piezoelectric buzzers have a frequency of approximately 3800 Hertz meaning that the piezoelectric element is flexing 3800 times per second. It is flexing such a little distance that you cannot see it, but you can lightly feel it! 

Why Do We Add Salt to the Conductive Dough?

Squishy Circuits uses conductive dough to move electricity (electrons) from our batteries through the components. The conductive dough allows these electrons to flow because it contains salt and water! You may have heard that water and electricity shouldn’t mix, but did you know that pure water is actually a good insulator – meaning that electricity cannot flow through it easily? Pure water (distilled or deionized) is made of hydrogen and oxygen and these elements are bound together and are electrically neutral So, if you try to pass electricity through pure water, it cannot pass through. 

However, very rarely do we have access to truly pure water. Most water has dissolved impurities such as minerals and salts and they can conduct electricity when they’re in water. So, it’s best to avoid combining electricity and water (unless you’re using Squishy Circuits of course!). We add table salt to our conductive dough to increase the amount of electricity that can flow and keep our circuits powered.

That’s the quick answer, but to fully understand let’s dive even deeper (and get a lesson in chemistry!)

Water molecules are made of hydrogen and oxygen atoms. Hydrogen has a +1 charge and oxygen has a -2 charge. To remain electrically neutral there are two hydrogen atoms for each oxygen atom. Hence, the abbreviations, H20 that you may have seen. Despite being electrically neutral, water molecules are uniquely shaped (like a Mickey Mouse head) such that they have a positive and negative side. This means they are ‘polar’.

Salts are made of a positive and negatively charged ion. In Squishy Circuits we use table salt which is made of Sodium (Na+) and Chlorine (Cl-). They combine to make NaCl which is also electrically neutral since Na has a +1 and Cl has a -1 charge (last time you sprinkled salt on your food it didn’t shock you!). But, once you add a salt into water, the polar water molecules arrange themselves so that they pull the salt molecule apart into Na+ and Cl- ions.

When using Squishy Circuits, the two terminals of the battery holder create a positive and negative side of the conductive dough. The Na+ ions are attracted to the negative side, and the Cl- ions are attracted to the positive side. This causes the ions to begin to flow in opposite directions.

It may seem that the movement of ions should cancel each other out, but remember that they have opposite charges. So, the positive ion moving in one direction and the negative ion moving the opposite direction (but with an opposite charge) causes their movements to actually cause a net positive electrical current flow. 

This positive flow is the same as flowing electricity and completes our circuits!