Archive for the ‘Science Activity’ Category

Hands-on-Science: Make a simple motor

Sunday, July 31st, 2011

Electric Motors are used in so many real-world applications.  In fact, you can see them being used in household items such as fans, refrigerators, washing machines and vacuum cleaners.   An electric motor uses electrical energy to produce mechanical energy, while a generator (or dynamo) uses mechanical energy to produce electrical energy.  Let’s build a simple motor to understand the basic science principles behind it.

 

 

 

 

 

What do you need?

Instructions

  • Step 1 – Prepare the coil using the wire
    • This is the part of the motor that moves. Starting about 3 inches from the end of the wire, wrap it 25-30 times around a AAA battery to form a coil.  Leave the tail about 3 inches long on each end.
    • Now carefully pull the coil off of the form, holding the wire so it doesn’t spring out of shape.
    • To make the coil hold its shape permanently, we will wrap each free end of the wire around the coil a couple of times, making sure that the new binding turns are exactly opposite each other, so the coil can turn easily on the axis formed
      by the two free ends of wire, like a wheel
    • If this method of holding the coil together is too difficult, feel free to use scotch tape or electrical tape to do the job. The important thing is to keep the coil together, and to have the two ends of the wire anchored well, and aligned
      in a straight line, so they form a good axle.
  • Step 2 – Remove top half of the insulation from the tail ends of the coil
    • It’s a small and subtle trick that makes the motor work. Hold the coil at the edge of a table, so the coil is straight up and down (not flat on the table), and one of the free wire ends is lying flat on the table.
    • With a sharp knife, remove the top half of the insulation from the tail end.   Be careful to leave the bottom half of the wire with the enamel insulation intact.
    • The top half of the wire will be shiny bare copper, and the bottom half will be the color of the insulation.
    • Do the same thing to the other tail end, making sure the shiny bare copper side is facing up on both wire ends
  • Step 3 – Prepare support for the coil
    • Straighten the larger loop of each paper clip.  This will form the support for the coil.
    • Hold one support to each end of the D cell.  This is done so electricity can flow from one support into the coil and back through other support to the battery. But this will only happen when the bare half of the wire is facing down, touching the supports. When the bare copper half is facing up, the insulated half is touching the supports, and no current can flow.
  • Step 4 – Insert battery in the base, connect supports and attach the coil
    • We will use the battery holder to hold the battery.
    • Attach the supports to the holes in the plastics at the end.
    • Insert the battery into the holder.
    • Set the coil tail ends in the paper clip support.
    • Place the magnet on top of the battery holder just underneath the coil. Make sure the coil can still spin freely, and that it just misses the magnet.    Adjust the coil so it spins close to, but doesn’t touch, the magnet.  Adjust the
      coil and the clips until the coil stays balanced and centered while spinning freely on the clips. Good balance is important in getting the motor to operate well.
    • Place a strip of paper between the battery and the electrical contact in the holder.  This is the on/off switch. Remove
      the paper to allow electricity to flow into the motor, and replace the paper when you want to stop the motor and save the battery.
  • Step 5 – Start the motor
    • Remove the paper
    • Give the coil a gentle push to get it going.
    • You have succeeded if the coil spins by itself for 10 seconds.  If it doesn’t start, try spinning it in the other direction. The motor will only spin in one direction.

What’s happening?

An electric motor uses electrical energy to produce movement or mechanical energy.  The key to understanding the electric motor is to know how electric current behaves in a magnetic field.  The operative principle in an electric motor is the same as an
electromagnet.

Electricity is created when particles become charged.  Some are negatively charged (electrons), some are positively charted (protons) and others have no charge (neutrons).  The opposite charges attract, while particles with similar charges repel each other.  Combining electricity with magnets makes an electric motor.  An electric current in a magnetic field will experience a force.

What makes a motor turn is based on the fact that magnetic fields produce physical force that can move things. If you have
ever played with magnets you have seen this in action as you use one magnet to attract another magnet or force it to move without touching it, depending on how you line up their poles. All magnets have a north pole and a south pole. Like poles repel each other and unlike poles attract each other.  So, in a motor, electricity is used to create magnetic fields that oppose each other and cause something to move.  For a detailed explanation, see How does an
electric motor work
.

Why does your hair stand on end at the Van de Graaff generator in the Museum?

The Museum’s Van de Graaff generator removes electrons from the large globe, giving it a high positive charge. If you stand on an
insulated plate and touch this globe, all parts of your body become positively charged, including your hair. Since like charges repel, every hair on your head is now trying to get away from every other hair. The best way is to stand straight up. Result – flyaway hairdo!

Resources

 

 

 

Hands-on-Science: Write a simple computer program

Tuesday, July 19th, 2011

Do you find computer programming daunting? Perhaps it doesn’t have to be when the folks at Microsoft are trying to make it fun and easy.   Let’s write a simple Small Basic program.

What do you need?

  1. PC

Instructions

  1. Download Microsoft Small Basic 1.0 and install it in your computer.  If the link doesn’t work, lookup Microsoft Small Basic and install the latest version available.
  2. Type “Small Basic” on the Windows Start button.  Launch the application by clicking on it.
  3. Once Small Basic is started.  Click on New.
  4. Click on Save.  Name the file “Sample”.
  5. Now write the following program.   This is a simple program that sets the background color to Red, adds a rectangle, a circle and text.  It also moves the text to certain position on the screen.   Once you have written all the program lines.  Click on Run.  What happens? What do you see?

GraphicsWindow.BackgroundColor = “Red”
paddle = Shapes.AddRectangle(120, 12)
ball = Shapes.AddEllipse(16, 16)
words = Shapes.AddText(“Hello Science Explorers!”)
Shapes.Move(words, 25, 30)

If all the instructions you have given to the computer are right, you should see the following output window:

Want to tell the computer to do other cool things? To learn more about it follow the links below.  There are other interesting samples available within the Small Basic guide:

http://msdn.microsoft.com/en-us/beginner/gg604844.aspx

 

 

 

 

 

What’s happening?

When you click on “Run” to run the program, behind the scenes, Small Basic is converting the high level statements to machine language, which then produces the results you see on the output window.

“Microsoft Small Basic puts the fun back into computer programming.  With a friendly development environment that is very easy to master, it eases  students of all ages into the world of programming.”

Small Basic 1.0 Blog Announcement:

http://blogs.msdn.com/b/smallbasic/archive/2011/07/12/small-basic-1-0-is-here.aspx

New Small Basic Home Page on MSDN:

http://msdn.microsoft.com/en-us/ff384126.aspx

Small Basic Teaching Curriculum in different languages:

http://msdn.microsoft.com/en-us/beginner/hh314609.aspx

E-Book content licensed for use on MSDN:

http://msdn.microsoft.com/en-us/beginner/hh308208.aspx

 

Hands-on Science: Surface tension

Monday, July 18th, 2011

In these fascinating water experiments you will learn how many paperclips you can add to a glass full of water.

 

 

 

 

 

 

 

What do you need?

  • Glass
  • Water
  • Box of paperclips

Instructions

  1. Fill the glass with water until it is level full
  2. Now make a guess how many paper clips can you drop in the glass without the water overflowing?
  3. Count the paperclips as you drop each in the glass
  4. Ask another family member to do the same and see if they could add more

What’s going on?

Believe it or not water is sticky – not sticky like glue – but water molecules are very attracted to each other. If you had a glass of water, then the water molecules in the centre of the glass would be attracted to the water molecules above them, below them and to the side of them. But the water molecules on the surface of the water do not have any molecules above them to be attracted to, so they become more attracted to the molecules to the side and below them – this causes surface tension.

Water molecules have a positive and negative charge like little magnets. the negative part of the water molecule is attracted to another water molecules opposite pole where they stick together.  The attraction of water molecules to other water molecules is called cohesion. The force of the cohesion allows water to form a small dome over the top of a glass as you add the paperclips without overflowing.

Bonus Question: Can you make the paper-clip float? See answer here.

Hands-on-science: Make old pennies new again

Monday, July 18th, 2011

Have you seen rust on metals? Have you noticed rust on the old bridges? Or even old tools? Here is another fun activity that can be tried with basic household objects with your kids to teach them basics of metal reactivity.


What do you need?

  • 20 dull, dirty pennies
  • 1/4 cup white vinegar
  • 1 teaspoon salt
  • A clear, shallow bowl (not metal)
  • 2 clean steel nails
  • 1 clean steel screw
  • Paper towels

Caution

Be careful with the nails and screws!

Instructions

PART 1

  1. Put salt and vinegar in the bowl. Stir until the salt dissolves.
  2. Put one penny half way in the liquid and hold for 10 seconds.  Take it out of water. What do you see?
  3. Dump all the pennies in the bowl.  You will see them change color for few seconds and then it stops.
  4. Wait 5 minutes and take half of the pennies out of the liquid. Put them on the paper towl to dry.
  5. Take the rest of the pennies out of the bowl and rinse them very well under the running water. Put them on another paper towel that is marked “Rinsed”.
  6. After about an hour, look at the pennies on the paper towels.  What’s happened to the ones you rinsed? What’s happened to the others? What color is the paper towel under the unrinsed pennies?
  7. Keep the liquid for Part 2 of this excercise.

What’s happening?

Rust is scientifically called oxidation, which occurs when oxygen comes in long-term contact with certain metals.  Over time, the oxygen combines with the metal at an atomic level, forming a new compound called an oxide and weakening the bonds of the metal itself.  If the base metal is iron or steel, the resulting rust is properly called iron oxide.  Rusted aluminum would be called aluminum oxide, copper forms copper oxide and so on.

Why did the pennies look dirty before I put them in the vinegar?

Everything around you is made up of tiny particles called atoms. Some things are made up of just one kind of atom. The copper of a penny, for example, is made up of copper atoms. But sometimes atoms of different kinds join to make  molecules. Copper atoms can combine with oxygen atoms from the air to make a molecule called copper oxide. The pennies looked dull and dirty because they were covered with copper oxide.

Why did the vinegar and salt clean the pennies?

Copper oxide dissolves in a mixture of weak acid and table salt-and vinegar is an acid. You could also clean your pennies with salt and lemon juice or orange juice or tomato ketchup, because those juices are acids, too.

Why did the unrinsed pennies turn blue-green?

When the vinegar and salt dissolve the copper-oxide layer, they make it easier for the copper atoms to join oxygen from the air and chlorine from the salt to make a blue-green compound called malachite.

If you want to oxidize a new copper yourself, you can follow these instructions.

PART 2

  1. Put a nail and a screw into the bowl with liquid. Immerse another nail half way into the liquid by leaning it to the side of the bowl.
  2. After 10 minutes, look at the color of the nails. Are they different color than before?  Is the leaning nail 2 different colors? If not, leave the nails in the bowl and check on them in another hour or so.
  3. What’s happening to the screw? You may see fizzing bubbles coming from the screw.  Leave it in the liquid for a while to see what happens.

What’s happening?

Why did bubbles come off the steel screw?

Each water molecule is made up of two hydrogen atoms and an oxygen atom. In an acid (like vinegar or lemon juice), lots of hydrogen ions (hydrogen atoms that are missing an electron) are floating around. In the chemical reactions at the surface of the screw, some of these hydrogen ions join and form hydrogen gas. The bubbles that you see coming off the screw are made of hydrogen gas.

How did the nail and the screw get coated with copper?

To understand how the nail and screw got coated with copper, you need to understand a little bit more about atoms. Atoms are made up of even smaller particles called protons, neutrons, and electrons. Electrons and protons are both electrically charged particles. Electrons are negatively charged and protons are positively charged. Negative charges attract positive charges, so
electrons attract protons.

When you put your dirty pennies in the vinegar and salt, the copper oxide and some of the copper dissolve in the water. That means some copper atoms leave the penny and start floating around in the liquid. But when these copper atoms leave the penny, they leave some of their electrons behind. Rather than having whole copper atoms in the liquid, you’ve got copper ions, copper atoms that are missing two electrons. These ions are positively charged.

Now add two steel nails and a screw to the mixture. Steel is a metal made by combining iron, other metals, and carbon. As you found out when you cleaned your pennies, your mixture of salt and vinegar is really good at dissolving metals and metal oxides. When you put the steel nail in the mixture, some of the iron dissolves. Like the copper atoms, each of the iron atoms that dissolves leaves two electrons behind. So you’ve got positively charged iron ions floating in your vinegar with the positively charged copper ions.

Originally, the steel nail was neutrally charged-but when the iron ions left their electrons behind, the nail then became neg-atively charged. And remember what we said way back at the beginning of this section: negative charges attract positive charges. The negative charges on the nail attract positive charges in the liquid. Both the iron ions and the copper ions are positively charged. The copper ions are more strongly attracted to the negative charge than the iron  ions, so they stick to the negatively charged nail, forming a coating of copper on the steel.

This activity is courtesy of Exploratorium.

Hands-on-Science: Make your own salt volcano

Thursday, July 14th, 2011

What do you need?

  • Glass Jar or Clear Drinking Jar
  • Glass
  • Vegetable Oil
  • Salt
  • Water
  • Food Coloring (Optional)

Caution

Be careful with the glass

Instructions

  1. Pour about 3 inches of water into the jar
  2. Pour about 1/3 cup of vegetable oil into the jar. When everything settles, is the oil on the top of water or underneath it?
  3. (Optional) Add one drop of food coloring to the jar. What happens? Is the drop in the oil or in the water? Does the color spread?
  4. Shake salt on top of oil while you count slowly to 5.
  5. Add more salt to keep the action going for as long as you want.

To see the science behind this activity, go to Exploratorium Science Explorer.

What did you learn?

DENSITY – Low density liquids will rise above the higher density liquids

While water often mixes with other liquids to form solutions, oil and water does not. Water molecules are strongly attracted to each other, this is the same for oil, because they are more attracted to their own molecules they just don’t mix together. They separate and the oil floats above the water because it has a lower density.  The food coloring only mixes with the water and goes through the oil to reach the water.

Real World Applications

Variation

Would you like to make your Lava Lamp bubble? How would you do that?

  1. Get a glass jar with lid or a tube and fill it 3/4 full with oil (use some cheap vegetable oil).
  2. Add couple of tablespoons of water to the tube.
  3. Add 10 drops of food coloring.
  4. Divide an Alka-Seltzer tablet into 4 pieces.
  5. Drop one piece into the oil and water mixture.  What happens?
  6. When the bubbling stops, screw the soda bottle cap on and seal with duct tape. Be sure the bubbling totally stops.  Did you notice the fizz? This will take a few minutes. Turn the test tube slowly back and forth to see your lava lamp flow.

Oil and water molecules are so attracted to themselves that they do not mix together, even though they will mix with other substances. Oil has a lower density than water so it floats on top. The food coloring only mixes with the water and goes through the oil to reach the water. The alka-seltzer reacts with the colored water to make bubbles of carbon dioxide gas. These bubbles attach themselves to the blobs of food colored water and causes them to float to the surface. When the bubbles pop and the carbon dioxide escapes, the blobs sink back to the bottom.