During Our Fieldtrip Last Week to the Museum of Nature and Science Your Scholars Saw A

2nd grade

Electricity

During our fieldtrip last week to the Museum of Nature and Science your scholars saw a science program titled “Electric Theater.” That introduced your scholars to the world of electricity. Tonight we are going to make a homemade flashlight!

How it works:

Electricity flows through metals or other conductive materials. When you connect the two ends of a battery with a conductive material, current flows through the circuit. If there is nothing in the circuit besides the battery and the conductor, the current flows very freely, resulting in a drained battery, a very hot conductor, and possibly a fire. This is often called a short circuit.

To prevent this, a circuit should include some sort of load or resistance to slow the current down. This is usually accomplished by making the current do some sort of work -- in the case of a flashlight, that work is lighting the bulb.

In this flashlight, we are using two batteries in series for a little more oomph. Just as two train locomotives together can pull a longer train, two batteries can do more work.

To turn the flashlight on and off, we open the circuit by separating the two strips of aluminum. If there is not a complete path from one end of the battery to the other, no current will flow.

Materials

·  1 cardboard tube from a roll of paper towels

·  1 flashlight bulb

·  Aluminum Foil (or some pieces of electrical wire)

·  Masking Tape

·  A flat piece of cardboard

·  Two "D" batteries

Construction

1.  Cut two circles from the flat piece of cardboard. These will be used as the ends of the flashlight. Cut a 1/2 slit in the center of one and carefully poke a hole in the center of the other. Take two pieces of aluminum foil and fold them 4 or 5 times until you have two long strips about 12 inches by 1/2 inch each. Cut the cardboard tube to just slightly longer than the length of the two batteries together.

2.  Slip one of the aluminum strips about 3 inches into the cardboard circle with the slit in it. Fold the short end of the aluminum so that it makes a small square bump. Insert the light bulb into the hole in the other cardboard circle. Carefully wrap one end of the other aluminum strip around the metal side of the bulb's base. Be sure that the aluminum does not touch the metal tip on the bottom of the bulb. Insert the two batteries into the cardboard tube. (Make sure the batteries both point the same way.) Figure 3 shows these parts.

3.  Fit the two cardboard circles on the end of the tube to hold the batteries in place. Make sure that the bottom tip of the bulb and the aluminum square touch the ends of the batteries. Tape the circles in place with the masking tape. Tape the aluminum strips along the side of the tube so that they meet and over lap about an inch or two. Leave the end of one strip free so that it can be bent back to avoid touching the other strip. See figure 4.

4.  Turn the flashlight on by pressing the two aluminum strips together. If it doesn't light up, make sure that:

o  the bottom aluminum strip is securely touching the bottom of the batteries,

o  the top strip is touching only the side of the bulb,

o  the bottom tip of the bulb is firmly touching the top end of the batteries,

o  both batteries are pointing the same way, and

o  the two aluminum strips are touching each other without any tape in between.

To turn it off, simply fold back one of the aluminum strips so that they no longer touch.

5.  Turn out the lights and have fun!

http://www.sinasohn.com/crafts/flash.htm

Your scholars also learned about static electricity. Here are some experiments to try at home!

What is Static Electricity?

Everything we see is made up of tiny little parts called atoms. The atoms are made of even smaller parts. These are called protons, electrons and neutrons. They are very different from each other in many ways. One way they are different is their "charge." Protons have a positive (+) charge. Electrons have a negative (-) charge. Neutrons have no charge.

Usually, atoms have the same number of electrons and protons. When the atom has no charge, it is "neutral." But if you rub things together, electrons can move from one atom to another. Some atoms get extra electrons. They have a negative charge. Other atoms lose electrons. They have a positive charge. When charges are separated like this, it is called static electricity.

If two things have different charges, they attract, or pull towards each other. If two things have the same charge, they repel, or push away from each other.

So, why does your hair stand up after you take your hat off? When you pull your hat off, it rubs against your hair. Electrons move from your hair to the hat. Now each of the hairs has the same positive charge. Things with the same charge repel each other. So the hairs try to move away from each other. The farthest they can get is to stand up and away from all the other hairs.

If you walk across a carpet, electrons move from the rug to you. Now you have extra electrons. Touch a door knob and ZAP! The electrons move from you to the knob. You get a shock. http://sciencemadesimple.com/static.html

Materials for experiments #1 and #2:

·  Balloons

·  Access to a sink

·  Thread

·  Puffed rice of wheat cereal

·  Tape

Experiment #1

Scholars will observe how water can “bend.” Gather around your sink. Turn on the faucet and let the water run about 1/8 inch thick. Rub a blown up balloon vigorously on hair or a sweater to charge the balloon. Slowly bring the balloon near (but not touching) the running water; the water will “bend.” The positively charged water is attracted to the negatively charged balloon and moves the water towards it- opposites attract.

Experiment #2

Your scholar will need a 12 inch piece of thread, tape and a table. Scholars will tie the piece of puffed rice to the end of the thread. Then they will tape the thread to the edge of the table so that the puffed rice does not hang close to anything else. Have your scholar predict what they think will happen when a charged balloon is brought near the puffed rice. Have your scholar charge the balloon by rubbing it on hair or a sweater. Then bring the balloon near the puffed rice and observe what occurs. (The puffed rice will swing to touch the balloon). Scholars should hold the balloon still until the puffed rice jumps away. Ask, “What happens when you try to touch the balloon to the puffed rice again?” Scholars should observe that the puffed rice will move away as the balloon approaches. When you charged the balloon, electrons moved form your hair or sweater to the balloon; the balloon had a negative charge. Being neutral, the cereal was attracted to the balloon. When these items touched, electrons slowly moved from the balloon to the cereal. With both objects having the same negative charge, they repelled.

From the Educator’s Reference Desk: http://www.eduref.org/Virtual/Lessons/index.shtml

Materials for experiment #3:

·  1 paper towel

·  1 piece of plastic wrap about 12 inches square

·  Different objects from your house such as: pins, glitter, erasers, paper clips, etc.

·  Paper to record observations

Experiment #3

Lay the plastic wrap on a table. Charge it by smoothing it flat and rubbing it with the paper towel. Lift the plastic wrap off the table by one corner. What happens? (It’s attracted to the desk, then your arm. When you rubbed the wrap with the paper towel, electrons were transferred leaving the plastic wrap with a charge. It was attracted to the desk and then your arm.)

Lay it back down on the desk and charge it again by rubbing it with the paper towel. This time pick it up in the center, on opposite sides. What happens? (It looks like a tent or an upside down V. Since the surface has the same charge, and like charges repel, it is pushing away from itself.)

Now let’s see how statically charged objects affect other objects. Choose some of the small objects listed in the materials section (erasers, paper clips, etc). Charge the plastic wrap again. Then have two people take the plastic wrap on opposite ends, turn it over so the charged side is above the object, and hold it over the object. Lower it slowly until it’s about 2-3 inches above the object. What happens? Record it on a sheet of paper.

Select the next item to be tested and repeat the process.

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