Materials
Batteries (I used 1.5v, but a 9v or a 12v would work fine if you have the right bulbs)
Flashlight bulbs
Bulb holders (you can make your own out of thumbtacks, wire, and a small piece of wood)
Alligator clips -or- two pencils with thumbtacks inserted into the eraser and wire wrapped around the end
Insulated wire
Items to check for conductivity (coins, nails, plastic, styrofoam, wood, cloth, paper clips, etc.)

Procedure

Background
Since most of the students will have little or no experience with electricity, begin by explaining a few terms such as voltage, current, conductivity, insulators, and capacitor.  The analogy I like to use for younger students is comparing electricity to a water hose (it's not exact, but it's an easy way for them to picture it).  The pressure in the water hose is the voltage.  If you turn the water hose up, it has a higher pressure.  If you have more voltage, you have a higher "pressure."  Current is comparable to the width of the hose.  The wider the hose, the more water goes through it.  The more current, the more electricity can flow.  A capacitor is like a water tank and can be simply described as a battery, since it stores electricity.  If the students know what electrons are, draw a picture showing how they "bump" into each other moving only short distances.  The higher the conductivity, the more collisions occur.

Enough talk...let's test something!
The first experiment involves testing the conductivity of items.  Have the students write down which items they think are conductive on the "scientific method" sheet.  Using the battery, bulbs, and alligator clips, create a circuit.  Have each of the groups test a metal object to ensure each of the circuits is active.  Then let each group test the objects and see how they compare to their initial guesses.  Make sure you have multiple types of coins, because many of the students will assume that all metals conduct electricity equally.

Series vs. parallel circuits
Now, have the students connect another bulb to the circuit and see if they can get both bulbs to light up.  Many will notice that the bulbs will become dimmer when both are connected.  Ask them to explain why.  If you wish, and it's an advanced group, you might want to explain Ohm's law.  When completed, tell the students that they have created a circuit that is in series.  Now ask them to unscrew one of the bulbs.  What happens?  How would this be a problem if the electrical system in your home were hooked up this way?  Next, ask them to see if they can find another way to hook up the circuit so that when one bulb is unscrewed, the other bulb stays lit.  Walk around and help the students only if they become really frustrated.  In most cases, one of the groups will find a way to put the circuit in parallel.  You can then have members of that group walk around and help the other groups.

A side project for motivated students
Lake Linden Elementary purchased numerous crystal set radios.  These radios have easy-to-use instructions and checklists that would be wonderful science projects for gifted or motivated students.  No soldering is required, and little supervision would be needed.  You might have to explain what a diode or variable capacitor is.
 

Shawn Len, 2000.
HOME
INDEX