Teacher Notes for Electricity is Exciting



Teacher Notes for Electricity is Exciting

Contact information:

Cynthia Furse

Associate Professor

Dept. Electrical and Computer Engineering

50 S Campus Drive 3280 MEB

University of Utah

Salt Lake City, Utah 84112

Phone: (801) 585-7234

Fax: (801) 581-5281

ece.utah.edu/~cfurse

Overview:

This projects has the students measure and build a simple resistive circuit with a light emitting diode (LED – a tiny green lightbulb). This project is ideal for 5th grade classes, because it covers several of the major concepts in the Utah Science Core curriculum. It is also suitable for grades 3-8 (perhaps higher if done as part of a larger learning unit).

Concepts Covered:

Voltage

Current

Resistance (parallel and series)

Current paths

Math concepts Required:

Addition and multiplication of numbers with decimal points. The math can be eliminated for younger grades without reducing the effect of the project.

Length of Time Required:

In my experience, a class of 5th graders takes about 45 minutes to complete this unit, including the calculations. We allow 1 hour and use the remainder for discussion and questions. IF the calculations are eliminated, the project can be done in 25-35 minutes.

How many people should help/classroom setting:

A single teacher can help the class work through the entire unit. When I do this, I try to group the desks in a circle or large groups, so that I can easily walk between groups of students. Then I start at the first step and walk the class through each step as a group. Expect and encourage “noise” and talking when the students are working, so have a sign for “listen for the next set of instructions”.

Students should work in groups of 2 ideally, 3 maximum. Avoid putting girls working with boys, as the boys most often dominate the hands-on activity.

If you are able to acquire an extra parent or two for this project, it is even easier. The hard parts that a parent can help with are:

• Taping the batteries together (a few kids will be clumsy with this and not make good contact)

• Taping the wires on the ends of the battery (have one of the kids in the pair hold them tightly pressed together (not difficult, once they realize they can work together)

• Putting the resistors in series. They will most often “skip” a row on the circuit board, and the resistors don’t electrically connect. (This is the most likely thing for YOU to do wrong too, so if your resistors don’t connect, look carefully at the drawings in the handout.) When the students are doing this part, I just move between groups, helping them get them connected correctly. If you help every other group in a row, the kids will start to help each other in between, which they like to do, and which saves you time.

Student mentor-teachers:

As an experiment, I tried teaching one class, and having them help subsequent classes and younger (3rd grade) classes. The students LOVED it, and it was highly successful. I think the students who functioned as teachers learned a WHOLE LOT, too. If you have time (library time?) where one class is occupied, and you can “borrow” an extra teacher to help with this first class, you will have an automatic pair of extra hands for the first class, and a whole set of extra hands for the second.

Equipment Required:

Put the following in individual ziplock bags in preparation for your class:

Half-size breadboard

2 – 100 ohm 1/8 watt resistors

2 – 1000 (1k) ohm 1/8 watt resistors

1 LED (light emitting diode)

2 – AA batteries (C or D will also work)

You can get AA batteries free from places that process film. The instant cameras with flash have 2 batteries each. Usually they will take them apart for you. If YOU do it, wear leather gloves or use tools with plastic handles, and don’t touch the metal. If the capacitor was left charged after the last use, and you short across the batteries, you will get an unpleasant (though not deadly!) shock. Just use proper equipment, and you won’t have that problem. TEST all batteries in advance with the multitester (they should be 1.5 V), and discard any that are low.

2 pieces of wire, about 6” long, ends stripped.

Phone wire or other wire about 22 gauge is good.

STRIP both ends of wire (remove the plastic insulation) about ¾ inch from the end BEFORE your class. It takes time, the kids can’t do it well, and they won’t wait well!

Each group also needs:

1 electrical multitester

Available from Harbor Freight, the cheapest place I have found to get them.

Don’t use these to demonstrate on wall sockets, I wouldn’t trust them with anything other than batteries.

Prepare before your class (and discard when done):

1 potato, cut in half

2 AA batteries (taped together)

2 wires (ends stripped), taped on opposite ends of the battery

“Plug” the free ends of the wires into the white cut side of the potato about 1” apart.. Within 2-5 minutes, you should see tiny bubbles from one of the wires. Leave it overnight. In the morning, one connection point will be gray, and the other will be green. (There are just small spots, not giant ones.) The green spot shows copper ions from the wires being pushed into the potato by the current. The gray spot (where the bubbles were) is the potato ions being “pulled” towards the copper wire, thereby being exposed to oxygen, and turning gray (“spoiling”).

Class Preparation:

Before you try this with a class, do the whole student experiment yourself. If you don’t get what you think you should at each point, look carefully at the pictures, as you probably have something hooked up incorrectly or a dead battery.

Safety:

There is not very much you can do to be unsafe with this project. If the students deliberately short circuit the battery, by taping or connecting a wire between the two terminals of the battery, the wire will get hot, and if left long enough could burn them or eventually make the battery leak or worse. I have never had students try this, and I don’t mention it to them (because they then would (), but just watch for it.

The most important thing!!! Is to warn them that the power in the battery is safe for them to use, but the power in the wall is NOT. They should never try electrical experiments with power from the wall. Tell them that even electrical engineers do not. They also should not experiment with any device that plugs into the wall.

UTP&L has a coloring book for kids on electrical safety that is ideal for 3rd graders, and might be a little simple for 5th graders.

Going Further:

There are several teacher links on electricity on ece.utah.edu/~cfurse (click K12), electrical engineering careers, etc. Most libraries also have good science books with additional information and experiments on electricity. The equipment in your kit can be adapted to include electromagnets, to build a small electric motor, to add a paper clip switch, etc.

If you have a few excited students who want to experiment further (which has generally been the “rule” rather than the exception), encourage them to buy a kit from radio shack, the toy store, or one of the toy store links on my webpage, etc.

Have those kids help with tomorrow’s class in Mrs. X’s room.

Also, both boy and girl scout programs have badges for electricity, and since these programs are strong in Utah, I have sometimes linked those kids with the proper mentor, and they have done a lot on their own. Even if the kids aren’t in boy scouts, call the local office, find the electricity merit badge mentor, and see if they will take a spare kid. Usually they are glad to.

Integration with other parts of the curriculum:

Don’t miss out on the opportunity to add extra spelling words (resistor, resistance, parallel, series, voltage, current, electrical engineering, electrician, etc.).

If you are studying American history, consider reading about Tesla, Edison, Bell, and Franklin. Talk about the current path in Franklin’s kite.

IN art, draw resistive networks ( you can use different colors to indicate different resistances). Borrow some schematics from an electrician, or find them for your school, and see if you can find ways to make them easier to read and understand using color and codes.

In math, do “resistor math” to add and multiply numbers with decimal points. Challenge students to draw more and more complex resistive networks and determine their total resistance. You can buy a variety of resistors very cheaply, and have a hands-on tool to test it out. (If you get confused, call me.)

IN math, have students record the number of hours they spend doing different things with electricity. Graph/add/average it over the class. Calculate average, standard deviation, and peak use. Talk about electrical power distribution and the rate schedule that goes up during peak use time. Talk or write about its impact on the environment. Have the students do a service project to review their family’s energy use and educate them about turning off extra lights, etc.

Write about life without electricity. Or do a science fiction story about life in the future and all of the things that can be powered by electricity. Draw a picture showing the “cool kid” of the year 2010 (wrist watch or smaller cell phone, personal TV glasses, etc…. get creative), and how much of that cool stuff takes electricity.

What to do if you get stuck:

Just call or email. See above. (

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