Electricity Week 3

This fantastic example of creativity can be found here: http://www.abc.net.au/science/articles/2012/04/17/3479415.htm#.UceaMc4vD8t

Play dough circuits

First you need to make your dough. You will need salt play dough

	Cute little illuminated sculptures is where we're heading, but let's get started with some basics. You'll need a few light-emitting diodes, a battery pack, and two types of play dough: ordinary conductive play dough, which you can buy or make yourself (see instructions below), and non-conductive play dough, which you'll need to make (see instructions below).
	Light-emitting diodes (LEDs) LEDs are cheap and they're available from most electronics suppliers. The flexible legs make them perfect for poking into play dough. Grab a variety of colours while you're there.
	Batteries To power the LEDs, you need a 4 by AA battery pack. You'll need to solder terminals onto the leads for better electrical contact with the play dough. All these parts are available where you buy LEDs. And, who knows, they might even solder the terminals on for you. Doesn't hurt to ask, right?

How to make conductive play dough

	1.Ordinary play dough from the toy store conducts electricity and works fine, but you can also make your own with this standard play dough recipe. In a saucepan, completely dissolve half a cup of salt in 1 cup of warm water (dissolving the salt first ensures a good texture). Add your favourite food colour. Next, add 3 tablespoons cream of tartar, 1 tablespoon of vegetable oil and 1 cup of plain flour. Stir thoroughly.
	2. Cook the play dough mixture on low heat, stirring constantly with a wooden spoon until a ball forms (it takes just a few minutes). Place the ball and flatten it out on a lightly floured baking tray to cool (again, just a few minutes is enough).
	3. Knead in more flour until the dough stops feeling sticky and you're done. Like play dough from toy stores, this batch will conduct electricity nicely.

How to make non-conductive play dough

	1. Use demineralised water instead of tap water if possible (available from supermarkets and grocery stores). Mix 1 cup of plain flour and half a cup of white sugar in a mixing bowl (caster sugar works even better). Add 3 tablespoons of vegetable oil and mix thoroughly. Now add one tablespoon of water at a time until the dough forms baked-bean sized clumps.
	2. Transfer the lumpy dough onto a baking tray (not floured yet) and knead into a ball. Add more water, one tablespoon at a time and knead. Continue adding water until the dough becomes sticky. Now knead in more flour until the ball stops feeling sticky and reaches the texture of play dough.
	3. The non-conducting dough isn't quite as 'smooth' in texture, but can still be sculpted and rolled like normal play dough. Most importantly, it won't conduct electricity at the low voltages we're using. Store this dough in the fridge when not in use.

Making circuits

	A simple circuit Make two lumps of ordinary conducting play dough and poke one of the battery pack leads into each lump. Now poke one of your LEDs legs into each lump. Electricity only flows through LEDs in one direction so, if the LED doesn't light up, take it out, turn it around and poke the legs back into the lumps.
	Short circuits While the lumps are separated, the only way for electricity to flow through the circuit is to go through the LED, so it lights up. Push the two play dough lumps so they're touching each other, however, and the LED stops shining because you've created a short circuit. The conducting play dough has much lower electrical resistance than an LED. In a short circuit, the electricity flows through the play dough and bypasses the more resistive LED.
	Preventing short circuits Use the non-conducting dough to prevent the two lumps of conducting play dough from touching each other. The non-conducting dough has much higher electrical resistance than both the LED and conducting play dough, so now the electricity flows through the path of least resisance, which is through the LED.

Now you know how to light up the LED, start experimenting and next time, I'll show you how to build and illuminate some groovy play dough sculptures.

What's going on?

Salty water conducts electricity, which makes ordinary play dough a reasonably good conductor. Sugary water doesn't conduct electricity nearly as well. Replacing the salt in play dough with sugar produces dough that conducts so poorly at low voltages that it functions like a non-conducting insulator. Normal tap water, however, contains trace quantities of dissolved minerals that act like salt. That's why demineralised water will improve the insulating properties of your non-conducting dough.

Have the children write down the experiment with pictures in the last triangle on their page.

Electricity Week 2

Monday:

HOW DOES A BATTERY WORK?

Energy cannot be created or destroyed, but it can be saved in various forms. One way to store it is in the form of chemical energy in a battery. When connected in a circuit, a battery can produce electricity.

Batteries convert Chemical Energy into Electrical Energy

A battery has two ends -- a positive terminal (cathode) and a negative terminal (anode). If you connect the two terminals with wire, a circuit is formed. Electrons will flow through the wire and a current of electricity is produced. Inside the battery, a reaction between chemicals take place. But the reaction takes place only if there is a flow of electrons. Batteries can be stored for a long time and still work because the chemical process doesn't start until the electrons flow from the negative to the positive terminals through a circuit.

 

Have the children copy the diagram of the battery and its points.

Tuesday: 

What are the different types of batteries?
Different types of batteries use different types of chemicals and chemical reactions. Some of the more common types of batteries are:

Alkaline battery

Used in Duracell® and Energizer® and other alkaline batteries. The electrodes are zinc and manganese-oxide. The electrolyte is an alkaline paste.

Lead-acid battery

These are used in automobiles. The electrodes are made of lead and lead-oxide with a strong acid as the electrolyte.

Lithium battery	These batteries are used in cameras for the flash bulb. They are made with lithium, lithium-iodide and lead-iodide. They can supply surges of electricity for the flash.
Lithium battery	These batteries are used in cameras for the flash bulb. They are made with lithium, lithium-iodide and lead-iodide. They can supply surges of electricity for the flash.
Lithium-ion battery	These batteries are found in laptop computers, mobile phones and other high-use portable equipment.
Nickel-cadmium or NiCad battery	The electrodes are nickel-hydroxide and cadmium. The electrolyte is potassium-hydroxide.
Zinc-carbon battery or standard carbon battery –	Zinc and carbon are used in all regular or standard AA, C and D dry-cell batteries. The electrodes are made of zinc and carbon, with a paste of acidic materials between them serving as the electrolyte.

Show the children examples of each battery where possible.

Have children draw the batteries and their uses.

Wednesday:

Creating a battery from a lemon is a common project in many science text books.  Successfully creating one of these devices is not easy.
Batteries consist of two different metals suspended in an acidic solution.  Copper and Zinc work well as the metals and the citric acid content of a lemon will provide the acidic solution.
Batteries like this will not be able to run a motor or energize most light bulbs.  It is possible to produce a dim glow from an LED.
The picture at the top of this page shows a basic lemon battery, a lemon, copper penny and zinc coated nail.
The lemon:  A large, fresh, "juicy" lemon works best.
The nail:  Galvanized nails are coated in zinc.  I used a 2" galvanized common nail.
The penny: Any copper coin will work.






Creating the battery:  Insert a penny into a cut on one side of the lemon.  Push a galvanized nail into the other side of the lemon.
                                The nail and penny must not touch.

This is a single cell of a battery.  The zinc nail and the copper penny are called electrodes. The lemon juice is called electrolyte.
All batteries have a "+" and "-" terminal.   Electric current is a flow of atomic particles called electrons.    Certain materials , called conductors, allow electrons to flow through them.  Most metals (copper, iron) are good conductors of electricity. Electrons will flow from the "-" electrode of a battery, through a conductor,  towards the "+" electrode of a battery.  Volts (voltage) is a measure of the force moving the electrons. (High voltage is dangerous!)
 
 








I have connected a volt meter to our single cell lemon battery. The meter tells us this lemon battery is creating a voltage of 0.906 volts.
Unfortunately this battery will not produce enough current (flowing electrons) to light a bulb.
 
 


To solve this problem we can combine battery cells to create higher voltages.  Building more lemon batteries and connecting them with a metal wire from "+" to "-" adds the voltage from each cell.

The two lemon batteries above, combine to produce a voltage of 1.788 volts.  This combination still does not create enough current to light a small bulb. Note the red wire connecting the batteries is joined from "+" (penny) to "-" (galvanized nail).

Four lemon batteries create a voltage of 3.50 volts.  We should be able to light up a small device like an LED (Light Emitting Diode).
Note the connecting wires go from "+" to "-" on each battery.

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LED
To turn on an LED you must determine the "+" and "-" connections.  If you look closely at the red plastic base of an LED you will notice a "flat" spot (indicated by arrow above).  The wire that comes out beside the flat spot must connect to the "-" side of a battery, the other wire to the "+" side.

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Important information about LEDs:  LEDs are designed to work at very low voltages (~ 2V) and low currents.  They will be damaged if connected to batteries rated at over 2 volts.  LEDs require resistors to control current when used with batteries rated at over 2 volts.  Lemon batteries produce low current. It is OK to connect an LED to a lemon battery.

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In the above image, electrons flow from the "-" (nail) end of our lemon battery through the LED (making it glow) then back to the "+" (penny) end of the battery.  This is an electronic circuit. The LED glows dimly with this configuration.

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Improving your battery. The quality of the copper and zinc can be a problem for a battery like this.  Pennies in particular are rarely pure copper.
Try substituting a length of 14 gauge copper wire (common house wire) for the penny.  Experiment with different lengths and configurations of electrodes.  Other sources of zinc and copper may be found in the plumbing supply department of a hardware store.
The first battery was created in 1799 by Alessandro Volta .  Today batteries provide the power for an amazing variety of devices, everything from flashlights to  robots, computers, satellites and cars. Inventors and researchers continue to improve the battery, designing batteries that last longer and that are more friendly to our environment.
Understanding how batteries actually work requires a knowledge of chemistry.  The most important factor in battery design is the electrical relationship between the two metals used in the battery. Some metals give electrons away while other metals accept extra electrons.   Chemists have investigated metals and created an "electric potential" table comparing different metals.

 Thursday:

Why recycle batteries?

Batteries are made from important resources and chemicals, including lead, cadmium, zinc, lithium and mercury. Each battery placed in the recycling box will be taken apart and many of the materials will be recovered and used to make new batteries or something else.
If you put your batteries into a rubbish bin they will be taken to landfill sites and the resources lost.
Recycling batteries is good for the environment. It keeps them out of landfill, where heavy metals may leak into the ground when the battery casing corrodes, causing soil and water pollution.
If batteries are incinerated with household waste, the heavy metals in them may cause air pollution.

Have the children draw up why they should recycle batteries and why.

Electricity Week 1

Prep:
Have this template printed out for the week's use:

Also print out these activities:

Monday:

What is Electricity?

 

Give children brief explanation on process, something along the lines of:

Electricity is caused by flowing electrons.  Our children are not familiar with atoms, so draw them a picture (5,000 atoms on the head of a pin?).  The center of the atom has protons (+) and neutrons (no charge).  Electrons (-) circle around the nucleus of the atom.
If you rub a balloon on your hair, some of the electrons rub off the balloon and onto your hair.  The balloon is positively charged (because it now has more protons than electrons).  Your hair is negatively charged (because it now has more electrons than protons).  Opposite charges attract, which makes your hair stand on end when you hold the charged balloon close to it.  This is static electricity.
The electricity that flows through the wires in our homes is current electricity. Batteries use a chemical reaction to create current electricity.
For more information on electricity, check out the Magic Schoolbus and the Electric Field Trip.

Have children do the 'forms of energy work sheet.

Tuesday:

How do electric circuits work?

An electric circuit is like a pathway made of wires that electrons can flow through. A battery

or other power source gives the force (voltage) that makes the electrons move. When the 

electrons get to a device like a light bulb, your computer, or a refrigerator, they give it 

the power to make it work. 

The word "circuit" sounds like "circle," and a circuit needs to be circular to work. The wires

have to go from the power source to the device and back again, so that the electrons can go out

and come back.

Many circuits have a switch so that they can be turned on and off. When the switch is off, it 

makes a gap in the circuit and the electrons are not able to flow around. When the switch is 

turned on, it closes the gap and the electricity is able to move and make the device work. 

Have the children do the third work sheet.

Wednesday: 

This experiment is wonderfully worded here: http://frugalfun4boys.com/2012/03/19/electricity-experiments-for-kids/

To power a device such as a lightbulb, you need a circuit – an unbroken circle – for the electricity to flow through.
To make a circuit, you need copper wire, a 6 volt lantern battery, alligator clips, and a lightbulb.
*Note:  If you build your own circuit (without a neat lightbulb holder), you need to have one wire touch the very bottom of the lightbulb and the other wire touch the side of the lightbulb like this.  Otherwise, your lightbulb won’t light up.


A switch is simply a break in a circuit.  This switch came with our set, but would be really easy to duplicate at home with an index card, two metal paper fasteners, and a paper clip.  When the paper clip is touching both of the paper fasteners, the lightbulb lights up!  Move the paper clip away from one of the fasteners, and the light goes out.
Here is what the underside of the switch looks like.
The paper switch shows how a switch works, but I also bought a real light switch from Home Depot, and we hooked up the wires to that.  The boys had so much fun switching the switch and watching the light bulb turn on and off!

In their note page, in a triangle, have the children draw a picture of the experiment and a brief note on what happened and how it worked.

Thursday:


Most of the time electricity is safe. We have to watch out for dangerous electrical situations and know what to do.
We have to be smart, and careful, or we could be in for a big SHOCK.
As a class, discuss issues relating to electrical safety at home, school and outside.
Here are six things to get you thinking about how to be safe around electricity:

1. Be careful around electrical poles and wire when you play.
2. If you see a dangerous situation, tell an adult.
3. Electricity and water don't mix.
4. Stay away from substations.
5. Metal is a conductor for electricity and can be dangerous.
6. Know what to do in an electrical emergency.

Have the children do the second work sheet.