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.

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.

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.

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.

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.

HomeSchooling NotePages

Wednesday 3 July 2013

Electricity Week 2