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Conductivity Explorer

See how well various materials conduct electricity and use Science Journal to explore your data.

5 minutes for setup, 1+ hour for exploration

Tools and Materials

Body Conductivity

Suggested Materials

  • Beverages
  • Deionized water
  • Fruit, fresh and dried
  • Graphite pencil
  • Model Magic®
  • Potted plant
  • Vegetables

Facilitator Note

This activity offers open-ended experimentation with the conductivity of materials you can gather in your home or classroom, as well as the world around you.

As you explore, you’ll begin to notice patterns. What kinds of things are more conductive? Which are less so? We’ve provided a supply of suggested materials and questions to start with, but encourage you to go further and dig deeper.

Before beginning your investigation, you’ll need to build a conductivity meter to use with Science Journal.

See: Build a Conductivity Meter

Facilitator Note:

This activity offers open-ended experimentation with the conductivity of materials you can gather in your home or classroom, as well as the world around you.

As you explore, you’ll begin to notice patterns. What kinds of things are more conductive? Which are less so? We’ve provided a supply of suggested materials and questions to start with, but encourage you to go further and dig deeper.

Before beginning your investigation, you’ll need to build a conductivity meter to use with Science Journal.

See: Build a Conductivity Meter

Set Up: Build Your Probes

These conducting probes will make it easier for you to test materials with your conductivity meter.

1. Connect an arm’s-length piece of wire to your first lead on the breadboard using an alligator clip.

Longer wires help with giving you more mobility as you test later.

Body Conductivity

2. Repeat this step again for your second lead.

3. Wrap half of two skewers or craft sticks with aluminum foil.

These will become your new leads to test for conductivity with ease and efficiency.

4. Connect the two wires to your skewers or craft sticks using alligator clips.

Body Conductivity

5. Test your probes with Science Journal.

To do this, first pair your microcontroller meter setup to your smartphone. Once you’re connected, you can use either meter or graph modes to see your data.

With the two probes held apart, you should see a value of 0%. But when you touch the foil-covered ends together, you should see 100%.

If your probes pass these two tests, you are ready to start exploring.

Tip

While using your probe to make readings, make sure you aren’t touching the foil, as skin contact might interfere with your measurement. If you would like to test the conductivity of your body, check out Body Conductivity.

Warning: As you search for materials to test, remember not to include anything that’s electrically powered, as you may hurt yourself and/or your electronics. Your meter tests conductivity by passing electricity through objects; these electric currents are tiny, but could interfere with especially sensitive electronic circuits.

Try This: Banana Explorer

A banana isn’t just a delicious treat—it’s also a versatile subject for conductivity experiments.

Peeled or unpeeled, sliced or whole, bananas are fruitful subjects for electrical experiments. As you conduct your experiments, remember to record them in Science Journal so that you can go back to review your data later.

1. Brainstorm: Take some time to think about what you already know about conductivity.

Why do some things conduct electricity while others don’t? Can you think of any experiments you could do with your banana that would test your beliefs about conductivity, or further your understanding?

2. Explore: How conductive is your banana?

See how many different conductivity readings you can get from your banana.

For example, you might try changing the length of your banana or testing the fruit as well as the peel. Try placing your probes firmly on the surface or try digging them into the flesh of the fruit.

Change one variable at a time and see how your reading changes.

3. Take notes as you experiment.

Take notes either in Science Journal or on a piece of paper. Keeping track of your data will help you notice patterns and may spark other questions later.

Body Conductivity

4. Try testing other fruits.

You can use your banana observations to uncover similarities and differences with other kinds of fruit. Is there a difference between fruits with thick or thin peels? With seeds or without? Between juicy and dry fruits?

Body Conductivity

5. Now try other materials and begin your own exploration of conductivity.

Search your surroundings for other things to test—foods, pens, pencils, paper clips, clothing—the possibilities are endless. Use our suggestions here as starting points for your own questions and experiments.

Afterward, share and compare the data from your testing with other people. What readings surprised you? Were any of your assumptions about conductivity supported?

Graphite

Draw a circuit: Make a thick heavy line with a pencil, then touch your meter’s two alligator clips to either end. Experiment by lengthening or thickening the line, or drawing various shapes. Can you find locations on the line that correspond to specific readings, such as 20%, 50%, or 80%? Challenge: Try drawing a complex image with several lines and an assortment of readings.

Body Conductivity

Drinks

How conductive are the liquids you drink? Is all water equally conductive? What happens when you add small amounts of a sports beverage to cups of water? For a systematic study, try adding different amounts of a sports beverage to equal amounts of water, and then measure and record your observations.

Body Conductivity

Salt Water

Start with distilled water, add a pinch of salt, and watch what happens to a graph of the conductivity over time. Does stirring make a difference? Try adding more salt; how conductive can water get?

Body Conductivity

Food

Which foods conduct electricity? Which foods don’t? Compare foods that are sweet and salty, soft and hard, wet and dry. Also try fresh versus dried versions of the same food, such as plums and prunes. What patterns do you see in your readings if you string “modular” foods like potatoes or grapes together in a chain?

Body Conductivity

Clay Conductor

Make a playable instrument using Model Magic® clay and the sonification feature in Science Journal. To do this, roll out your clay and attach a probe to one end. Use the other probe to identify your other contact points, such as 20%, 30%, and 40% conductivity. Insert paper clips into these points to make your contacts easier to connect. Once you’ve enabled audio, you can use the free probe to play music.

Plant Moisture Monitor

Make an electronic reminder to water your plants using the threshold feature in Science Journal. Attach your meter to foil-wrapped skewers and stick them into the soil near the plant’s roots and get measurements before and after watering. Write these numbers down. Set a Trigger in Science Journal to tell you when moisture levels have decreased to the point that it’s time to water again.

Body Conductivity

What's Going On

The phenomenon we call electricity arises from the existence and motion of electrical charges: positive charge (protons) and negative charge (electrons).

When charges move, they create what’s called an electrical current. The “push” that forces charge is called electromotive force, better known as voltage, measured in units of volts.

While charges are “pushed” by voltages, they are simultaneously held back by resistance. A property of all matter, resistance is a measure (in units of ohms) of how much an object opposes the flow of an electrical current through it.

Your conductivity meter works by creating a voltage “push” between the leads and then detecting how much current flows as a result—a flow which depends directly on the resistance encountered along the way.

As you probably discovered in your explorations, most metals have a very low resistance, and electrical currents pass easily through them. Such materials are called conductors, and they owe their conductivity to the presence of “free” or loosely bound electrons, which are able to move easily from place to place.

Materials with high resistance are called insulators. Glass, wood, rubber, plastic, and air are all good insulators—they block the passage of electrical current. In these materials, electrons are more tightly bound within the atomic structure, and can’t easily move.

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Pure water is not a conductor, but when you add salts and other impurities to water, they dissolve into ions, atoms or molecules having electric charges. Ionic solutions are terrific conductors—something you may have noticed if you tested the conductivity of salt water.

Were you surprised to find that graphite is a conductor? This material we know as pencil lead is made up of flat sheets of carbon arranged in a honeycomb pattern. Considered a “semimetal,” graphite has free electrons that can carry current.