Monday, August 24, 2009

Electronics component sites

Electronics Component sites
www.ni.com
· www.signtec.com
· www.omega.com
· www.agilent.com
· www.temperatures.com
· www.microcontroller.com
· www.electronicscircuit.com
· www.kmitl.ac.th
· www.processregister.com
· www.scribd.com
· www.digital.ni.com
· www.edaboard.com
· www.ntworld.com
· www.cnx.org
· www.eng-tips.com
· www.8051projects.info
· www.globalspec.com
· www.wiley.com

POTATO BATTERY

POTATO BATTERY

Can a simple potato work as a battery to light a small light bulb?

INDIANA STATE STANDARDS ADDRESSED:
6.3.17 Recognize and describe that energy is a property of many objects and is associated with heat, light, electricity, mechanical motion and sound.

6.3.23 Explain that electrical circuits provide a means of transferring electrical energy from sources such as generators to devices in which heat, light, sound, and chemical changes are produced.

OBJECTIVES

Students will understand that all energy originates from the Sun.

Students will learn that electrical circuit flow is necessary in transferring energy from one source to another.

Students will generate hypotheses on whether a potato contains enough energy to light the bulb.

Students will be able to research, and test other objects to see if they contain enough energy to light a bulb.

MATERIALS

POTATO – one for each group
SMALL COPPER STRIPS (COPPER TUBING OR PENNIES MAY BE USED) – two for each potato
SMALL ZINC METAL STRIPS (GALVANIZED NAILS OR SCREWS MAY BE USED) – two for each potato
A LOW VOLTAGE LIGHT EMITTING DIODE (LED) – one for each group
CLOTHESPINS (OPTIONAL)
ALLIGATOR CLIPS – at least six for each group
ELECTRICAL WIRING (5-10 cm STRIPS) – at least three for each group

INTRODUCTION
Background Information
We know that batteries are used to operate many common devices. A battery is just a device that stores energy by using two metals that are not alike and a substance called an electrolyte, which is a material that allows ions to flow through it. Batteries convert chemical energy into electrical energy. To make a simple battery zinc and copper strips must be placed into an acid.
Think back to what you have learned about chemical reactions. We know that when two molecules collide they often cause a chemical reaction that produces a product. In many ways, this is how the battery works. When the zinc strip is placed into the acid it slowly dissolves which frees its electrons. At the same time the acid uses the electrons and the copper strip to form hydrogen gas. Because the zinc strip is freeing electrons and the copper strip is using electrons we can place a wire between the two strips and the electrons will flow from zinc to copper. This flow is electrical energy.
This information tells us that it may be possible to make a battery using materials that are found in many homes. Today we will test our hypothesis using the common potato. For our experiment the potato will act as the acid. By inserting zinc and copper strips into the potato we will be able to light a small light of less than 1.5 volts.

PREPARATION
Before beginning, alligator clips should be fastened to either side of the electrical wire. Some alligator clips have screws which can be tightened over the ends of the electrical wire. Others require the wire to be soldered to the clip.

PROCEDURE
1. Engage students in a discussion about what is needed to light a light bulb. Make sure that students understand that light is a form of energy, and that light energy must be converted from another source, such as a battery.
2. Ask students about their normal conceptions of batteries. (“What do batteries look like? What different kinds of batteries are there? etc.”) Surprise the students by suggesting that a potato can be a battery as well.
3. First you will need to get your potato. Make sure it is clean of all debris. Fresh potatoes will work better. Cut it in half for the students.
4. Locate your zinc and copper strips. Attach an alligator clip to one end. Be sure that the strips and clips are clean.
5. One zinc strip and one copper strip should go into each potato half. With the cut side of the potato facing down, push the end of the metal strips into the potato, about a finger length apart, or 3 cm depending on the size of the potato. You should still be able to see some of the strip sticking out of the potato.
7. Connect the remaining alligator clips to the base of the light bulb. Make sure they do not touch each other! As you connect both of them the light should begin to shine even if it is faint.
8. Observe your light. Write down how long it seems to be shining.
9. Discussion Questions:
- Where does the energy come from?
- How do batteries work? Why are we able to use a potato as a battery?

EXTENSIONS
- Have students locate other substances for use as electrolytes. Comparisons can be made relating degrees of brightness and the amount of time that the bulb is lit. Acidic substances such as citrus fruit or soda work well.
- Have students change the metals. Two like metals will not conduct electricity, because electrons cannot be exchanged.
- If available, use a light meter to determine the actual amount of light. Values can be graphed and compared in a quantitative manner.
- Have students diagram the pathways of the energy in the potato. This can focus either on the battery itself or the potato as it occurs in the food chain.