Introduction: It's Electrifying!!
I strongly believe that we LEARN best by DOING but getting the proper equipment into the hands of our budding "STEMist" has definitely been a challenge this year. One of the units in our Science course covers Static and Current Electricity, and this Instructable summarizes three activities that can be completed with household material. Our take-home electricity kits include:
- Building your own electroscopes to explore static electricity
- Building your own battery from pennies, aluminum foil and vinegar
- Building circuits using household items
Step 1: Build Your Own Electroscope
An electroscope is an instrument used by scientist to measure the relative strength of an electric charge. In this activity, we will build a simplified version of an electroscope to study and explore static electric charges.
- Clear Plastic Cup
- Paper Clip
- Aluminum Foil
- Push Pin
- Balloon/Plastic Comb/Cotton T-shirt/Wool Sweater
- Using the push-pin, create a small hole in the bottom of the plastic cup through which the paper clip will later be inserted.
- Cut two strips of aluminum foil that measures roughly ¼" by 1½". Use the end of a paper clip or push pin to punch a small hole in the end of each foil strip.
- Unfold the paper clip so it looks like a long J and hang the foil strips, called leaves, on the curved end of the J. Smooth out the leaves so they hang straight and next to each other, but do not press them together.
- Holding the cup upside down, insert the straight part of the paper clip through the hole so the leaves hang inside the upside down cup without touching the desk or table. Secure the paperclip with a piece of tape.
- Roll some aluminum foil into a ball and place the ball on top of the paper clip that is sticking out of the cup. The electroscope is now complete and ready for use.
Testing your electroscope:
We built our electroscopes after our lesson on charging by conduction and induction. Here is a good video from Flipping Physics: Charging by Conduction and Induction.
Part A: Charging Temporarily by Induction
- PREDICT: What will happen if you move a negatively charged object near the foil ball on the top of your electroscope?
- OBSERVE: Blow up your balloon and rub it vigorously against your hair, a cotton t-shirt, a wool sweater, etc. Bring the charged balloon CLOSE TO (BUT NOT TOUCHING) the foil ball. Observe what happens. Move the balloon away from the electroscope. Observe what happens.
- EXPLAIN: What made the leaves move? Why did they move back to the original position after you removed the balloon. Can you explain this using the concepts of charges and electrons? Think about how similarly charged objects behave.
Part B: Charging Permanently by Induction
- PREDICT: If you "ground" the electroscope by touching it with your finger, what do you think will happen?
- OBSERVE: Charge the balloon again and hold it near the ball. At the same time, touch the ball with your finger. Observe what happens. Now remove the balloon and your finger at the same time. Observe what happens.
- EXPLAIN: This is called charging by induction, as you have induced a charge onto the electroscope. How does charging perm
- Make sure your leaves are not stuck together. They should be two separate pieces that can move freely on the J part of the paper clip. If your leaves don't move, check if the leaves are wrapped around the paper clip. They should be able to move on their own.
- Try this on a dry day. Why does the humidity in the air matter?
- Matt Craig created an amazing Java-based electroscope simulation here.
Step 2: Build Your Own Battery/Voltaic Cell
How does a voltaic pile make electricity? The key to electricity is the movement of electrons. In a voltaic pile, electrons move from one metal to the other through the saltwater solution. The saltwater solution is called an electrolyte, and it contains ions in solution from the dissolved salts. An ion is a group of atoms that carries a positive or negative electric charge. The ions react with the metals, causing an electrochemical reaction, a special kind of chemical reaction that makes electrons. The two types of metals in a voltaic pile are called electrodes. Since there are two kinds of metals, one metal reacts more strongly than the other, which leaves an electrical potential difference, also called (voltage,) between the two types of metals. One metal becomes positively charged (cathode) and the other becomes negatively charged (anode). This causes electrons to move, creating an electrical current (which is measured in amperes), and then you have electricity!
Building a working battery from scratch is within the reach of everyone. In fact, with a few basic items, you can make a working replica of the world’s first modern battery, invented by Alessandro Volta way back in 1799.
- Paper towels
- 10 Pennies
- Cardboard/construction paper
- Kitchen foil
- Small Beaker/cup
- Stir rod/spoon
- Tape & 2 wires (optional)
*Use 10 Post-1982 US/1997-1999 Canadian OR 10 Pre-1982 US/pre-1996 Canadian Pennies
Steps: Watch: https://youtu.be/vIHfUJu3aKo
- Clean your coins. Put the coins into a beaker of vinegar and a scoop of salt. Stir with the glass stir rod for approximately a minute until they are nice and clean. Dry with a paper towel.
- Using a coin as a template, cut out nine cardboard circles. Soak the cardboard circles in vinegar, mixed with a little salt.
- Make nine foil circles – cut these a bit smaller.
- Build up a stack in this order: coin, damp card circle, foil disc. Continue until you run out of coins. Make sure the foil layers do not touch.
- Connect the LED by touching the longer lead to the penny and the shorter lead to foil disc. Make sure that the leads don’t touch any other layer. Did the LED turn on? If not, try adding an additional coin, card, foil layer to the bottom.
- If your LED does not light up, use the multimeter to measure the amount of voltage. Turn the dial to voltage (V) and touch the black lead to the foil and the red lead to the copper. If your reading is negative, swap the leads.
What’s going on?
Batteries are devices that convert chemical energy into electrical energy. When two different metals re connected by an electrolyte, a chemical reaction occurs at each metal surface that either releases or uses electrons. In the coin battery, each aluminum foil circle reacts with the acidic vinegar electrolyte to generate aluminum hydroxide on its surface along with an abundance of electrons. The excess electrons repel one another and escape from the metal along the wire. The moving electrons pass through the LED and round the circuit to the copper in the coins. The copper then serves to let the negative charge back into the electrolyte, thus replenishing the electrolyte and letting the reaction continue.
The oxygen that is dissolved in the electrolyte takes part in the electron transfer, and when it has been used up the electricity will stop flowing. Because there isn’t a lot of electrolyte in your coin battery, it will quickly run out – so use your LED wisely!
- BUT my battery isn’t working! Not all pennies are created equally! Post-1982 US and 1997-1999 Canadian pennies have zinc cores that are plated with copper. Pre-1982 US and pre-1996 Canadian pennies are 98% copper. The cardboard soaked in salty vinegar water serves as the electrolyte between the two terminals.
- Each coin-cardboard-aluminum foil stack represents one individual cell. By stacking additional coin, cardboard, foil stacks, you’ve created a battery, which is a series of electrochemical cells. This is also called a voltaic pile, which is named after Alessandro Volta, who created the first battery in 1800 by alternating zinc and copper electrodes with sulfuric acid between them. In Volta’s battery and your penny battery, an oxidation reaction occurs at the zinc electrode that releases electrons and a reduction reaction occurs at the copper electrode that uses them
- With a voltmeter, you can see that each cell can generate over 0.6 volts. The penny battery you created has nine cells. The total voltage is the number of cells x the voltage per cell. A stack of nine cells should generate enough voltage to light a LED, which usually require around 1.7 volts.
- Can we use different metals? Can we use different coins? Try replace the washers with dimes or nickels (nickle-plated)
- How does changing the number of cells change the voltage? 1 cell = penny + cardboard + washer
- Do the type of pennies matter? Can we use a mix of different pennies? Can we change the electrolyte? Or the material soaking up the electrolyte?
- How long will our battery last?
- Check out this TedEd video on How do Batteries work by Adam Jacobson
- Any other ideas?
Step 3: Scrappy Circuits
Scrappy Circuits is a KickStarter campaign that teaches you how to make take-home electrical components kits out of basic office supplies and dollar-store items! Check out: https://www.scrappycircuits.com/ for how-to videos, potential scrappy clips/wire options, electrical components (e.g. core brick) instructions, and the creators profiles!
- 9 binder clips
- 8 paper clips (must be uncoated)
- 4 wires (2 insulated & 2 copper) - Click here for other Scrappy Clips options
- Aluminum foil and other conductors/insulators
- Recommended: wire strippers & pliers
- 3V CR2032 coin battery*
*Scavenged from dollar store tealights - Check out this video walkthrough on how to take an LED apart.
We were able to build the following circuits with these kits and practice our circuit diagrams:
- A simple circuit with one LED and a cell/battery that can be used as a conductor/insulator tester.
- A simple circuit with one LED and a switch
- A circuit with two LEDs in series
- A circuit with two LEDs in parallel
Troubleshooting: We recommend building your core bricks in the following order.
- Use the coin battery to test your LEDs and identify the positive and negative legs. This confirms you have a working battery and LED.
- Build your wires next, and test your connections by touching them to the LED legs and the battery. This confirms you have good wires. If you are using insulated wires here, think about why it's important to have a good connection with the paper clip.
- Build your battery brick and LED bricks. Test by building a simple circuit with each LED.
- Build a binder clip switch or a push switch and add it to your simple circuit.
- Add in a second LED in series. If both your LEDs don't light up, try adding a second battery/cell.
- Rearrange your circuit so your LEDs are now in parallel. Try placing the switch in different positions to control both LEDs, and one LED individually.
- You can scavenge a lot of working electronic parts from dollar-store, broken or discarded items. We saved the switches from the LEDs so we could use them some other projects. You can find motors, buzzers and speakers in toys or fans.
- Can you put some of these components together to make an electronic greeting card?
- Scrappy Circuits has a bunch of other brick ideas here!
Grand Prize in the
Back to Basics Contest