# Find the Center of Gravity of a Body

### Aim:

The aim of this simple science fair project is to demonstrate the concept of center of gravity with a simple experiment.

### Materials required:

1.      A meter ruler or cane.

2.      Some clay.

### Procedure:

1.      Take the meter ruler and support it by two fingers at two ends.

2.      Slide your fingers towards each other slowly without unbalancing the ruler. They will meet under the center of gravity of the ruler.

3.      Attach some clay somewhere on the ruler.

4.      Support the ruler again by two fingers and repeat the experiment. You will see that your fingers will meet somewhere close to the lump of clay.

### Scientific explanation:

The center of gravity of an object is the average location where the weight of the object acts. In this experiment when you start off, one finger will be further from the center of gravity than the other. This finger will find it easier to slide across the ruler than the other as it is holding less weight. Hence when you slide two fingers towards each other, the one which is further from the center moves faster and the fingers automatically meet at the center of gravity. When you add a lump of clay to the ruler, the center of gravity shifts closer to the lump of clay and hence your fingers meet at a point closer to the lump of clay now.

# Different Weights for Same Volume of Soda!!!

### Aim:

To understand how even the same volume of liquid can have different mass and weight.

### Materials required:

1. A bucket of water.
2. A can of normal soda and diet soda of the same brand and size.

### Procedure:

1. Fill the bucket with water.
2. Drop the can of diet soda in it. You will see that it floats.
3. Now drop the can of normal soda of same volume in it. It will sink to the bottom.

### Scientific explanation:

Even though both cans have same volume of soda in it, there is one ingredient different between the two. Normal soda has sugar for sweetness whereas diet soda uses aspartame instead. Aspartame is 200 times sweeter than normal sugar and hence less aspartame is needed for the same amount of sweetness. Hence the mass of sweetener is less in the diet soda can than the other one. Since the weight is less, the can of diet soda floats while the other sinks.

# Static Charge Experiment with Rice Krispies

### Aim:

The aim of this science fair experiment is to demonstrate that static charge exists with the help of rice krispies.

### Materials Required:

1.      A plate of rice krispies.

2.      A bar of thermoplastic.

3.      A block of wood so that the thermoplastic can be placed 1-3 inches above the table.

4.      Some wool preferably a sweater.

### Procedure:

1.      Place the plate full of rice krispies on the table.

2.      Take the wooden block or for that matter any non conductive block and balance the thermoplastic bar on the block right above the plate of krispies.

3.      Then rub the wool on the thermoplastic, vigorously. Leave it as such. After sometime we see that the krispies would stand on its end and then ‘jump’ from the table to the thermoplastic and then drop back to the plate on which it was placed.

### Scientific Explanation:

This is the result of buildup of static charge. When we rub the wool on the thermoplastic it gets charged negatively. This in turn polarizes the rice krispies which is right below the charged thermoplastic. The krispies gets positively charge (polarization results in accumulation of opposite charges). And s we all know that unlike charges attracts. So as the polarization slowly takes effect, the charge difference keeps on increasing. As a result the krispies first stands on its end and later when the charge difference is sufficient the krispies jumps and sticks to the thermoplastic bar. As they both come in contact their respective charge neutralizes and the force of attraction vanishes. Then gravity comes into picture which pulls the krispies down as the static charge vanishes. The neutral krispies fall back to the plate.

# Conductivity testing device

### Aim:

To make a simple device to test the conductivity of objects and find out whether they are good or bad conductors of electricity.

### Materials required:

1. A small flashlight bulb.
2. A battery.
3. A shoe box.
4. Three pieces of wire, each around 10 cms long.
5. Duct tape.
6. Different conductors to be tested, such as a metal coin, a plastic comb, a piece of paper, a dish of water, etc.

### Procedure:

1. Make a small hole on the top of the shoebox and insert the flashlight bulb into it so that the protruding end goes into the box while the head of the bulb stays outside.
2. Tape the battery onto the bottom of the shoebox on the inside of the box.
3. Tape the end of a wire to the positive end of the battery and another wire to the negative end of the battery.
4. Connect the wire from the positive of the battery to the metal tip of the bottom of the bulb.
5. Tape one end of the third wire to the metal ring on the side of the bulb.
6. Connect the free end of this wire to the free end of the wire connected to the negative terminal of the battery. If the bulb light up, the connections are right and the device is ready.
7. Now connect the free end of the third wire and the wire coming from the negative terminal of the battery to different objects in turn. When connected to the metal coin you will observe that the bulb lights up. When connected to the plastic comb it will not light up. Thus you can distinguish the good conductors from the bad ones. When good conductors are connected to the device the bulb will light up. When the bad ones are connected, the bulb will either not light up or will light up feebly if the object is not a complete insulator.

### Scientific explanation:

The flashlight bulb lights up when the circuit is complete with the battery connected. When different objects are connected in the circuit, the circuit is completed only when good conductors are connected. When insulators like the plastic comb are connected, the current does not flow through the circuit and the bulb does not light up.

# Create a Simple Magnet

### Aim:

To make a magnet out off simple iron pieces.

### Materials Required:

1.      A magnet.

2.      Some iron pins.

### Procedure:

1.      Take the magnet and move it over the iron pins.

2.      Start it from the tip and run it to the other end of the pin.

3.      Keep doing it a number of times and make sure that you do it in the same pattern i.e. from the same end to the other. After sometime we see that the iron pin has become magnetic.

### Scientific Explanation:

This magnetic effect is short lived. It is because as we move the magnet over the pins the poles gets aligned as it is attracted by the poles of the magnet. This is just like the magnet. But it is short lived as the particles get distorted and loose alignment.

# Flickering Lights Science Fair Experiment

### Aim:

To conduct a simple experiment to understand the flickering effect of an LED bulb.

### Materials required:

1. A radio or any other device with an LED light. Or an LED bulb.

### Procedure:

1. Switch on the LED bulb.
2. Stand around 4 to 10 feet away from the bulb and observe the light.
3. Give a Bronx cheer. That is, make sound by blowing air through your lips and vibrating them. Observe how the LED light flickers.
4. Try shaking you head very fast and see if the LED light is flickering.
5. Do the Bronx cheer while looking at an incandescent light bulb and see if there is any flickering.

### Scientific explanation:

Even though an LED light bulb seems to give out light constantly when it is turned on, it actually flickers on and off sixty times a second. However this is so fast that your eye usually can’t notice when the bulb goes off. Hence you see it as continuous light. However when you do the Bronx cheer, your entire body vibrates and your eyes see the LED bulb from different angles. Hence the flickering is noticed as the image of the bulb falls at different points on your retina instead of at the same point. An incandescent bulb does not flash on and off and gives a steady glow throughout the time it is kept on. Therefore this flickering effect does not come into play when you give a Bronx cheer looking at an incandescent lamp.

# Make an Electromagnet Using an Iron Nail

### Aim:

The aim of this science fair project is to make a simple electromagnet using iron nail.

### Materials Required:

1. A long iron nail
2. A copper wire of length 1 meter (lightly insulated)
3. 1 or two cells of batteries
4. Paper clips

### How to Make the Electromagnet?

1. Remove the insulation at both the ends of the wire to a length of 2 centimeter.
2. Attach one end of the copper wire to the positive side of the battery
3. Closely wind the iron nail with the remaining copper wire but at least 10 centimeter of wire at the other end.
4. Now attach the free end of the copper wire to the negative end of the battery.
5. Bring the nail nearer to the paper clips. You can see that the nail is now a magnet and it attracts the paper clips.

### Scientific Explanation:

When current passes through a coil, a magnetic field is created around it. This field magnetizes the core which is the iron nail, and this in turn attracts the paper clips.

### How to improve your magnet’s strength?

1. The thicker the core is, the better.
2. The more closely the wire is wound together, the better
3. The tighter the wire is wound around the core, the better.

# Movement of Gas Molecules Demonstration

### Aim:

To understand and visualize the movement of molecules in a gas.

### Materials required:

1. A wire mesh cage, a bird cage will do.
2. Some ping-pong balls.
3. A few different colors of paint.
4. A blow dryer.
5. A paintbrush.

### Procedure:

1. Suspend the cage from the ceiling by a wire or rope.
2. Paint the ping-pong balls in different colors and put them in the cage after drying. Make sure you close the cage.
3. Hold the hair dryer under the cage and switch it on at low heat setting. Observe the movement of the balls flying around.
4. Increase the heat settings of the blow dryer. Observe how the movement of the balls increase.
5. Observe how the painted balls move around randomly and collide with each other. This is exactly how molecules move and collide in a gas.

### Scientific explanation:

All kinds of matter we see around us are made up of molecules. Not only solids and liquids, even gases are made up of molecules, even though they are not visible to our eye as they are less densely packed than in solids and liquids. Molecules are free to move around in a gas and move around randomly colliding with each other all the time. As the temperature of the gas increases, the energy of the molecules increase and their speed increases, hence leading to more random movement and collisions. In this experiment the air from the blow dryer simulate the behaviour of molecules of gas. As the temperature of the blow dryer increases, the balls move faster.

# Dancing Raisins Science Experiment

### Aim:

The aim of this fun science fair project is to show raisings jumping up and down in water.

### Materials Required:

1. A bottle of carbonated water (Soda)
2. 4 or 5 raisins (dry grapes)
3. A glass

### Procedure:

1. Fill half of the glass with the carbonated water.
2. Drop the raisins into the glass.
3. Wait for sometime and see the raisins dancing.

### Explanation:

We all know that soda (carbonated water) contains dissolved carbon dioxide. When kept open this dissolved gas escapes to the atmosphere. This gas gets collected in the uneven surfaces of the raisins and will raise them to the surface. As a result the raisin moves upward. On the surface the gas leaves the resins and escapes to the atmosphere. This causes the resins to sink again to the bottom of the glass. This process is repeated until all the gas in the glass has escaped.

Shadows never leave our sides like our best friends. They are with us always even if they have only one color. Is anyone think of painting them into some exciting colours? Human beings have always tried to make their world more colorful due to their fascination for colorful things. This may be the reason for the replacement of black and white TV to color and the color monitor to the monochrome. Turning our black shadows into colored ones is the next thing.

If we give two different colored lights to the same spot on a white screen, both the colors will shine at the same spot and the light reflecting from that spot to your eyes is called an additive mixture since it contains the colors from the same spot. By making additive mixtures using colored lights, we can learn about human color perception.

### Materials required for the Experiment:

1. A white surface. (Arrange a white wall or white paper taped to a stiff cardboard. Beaded or metal slide projection screen should not be used.)
2. We need green, red and blue light bulbs or flood lamps, one of each color. Clear-colored Christmas tree lights can be used. (For tabletop use smaller or dimmer bulbs are fine but larger or brighter bulbs allow a larger scale demonstration)
3. In order to make an arrangement for getting the light from the three bulbs simultaneously on to the same area of the white surface, we require three light sockets.
4. Any types of solid objects such as pencil, ruler, correction fluid bottle, finger etc are also required.
5. By doing this experiment, we are turning our black shadows into coloured ones.

### Procedure of the Science fair project:

1. The red, green and blue bulbs should be arranged in such a way that the light from all the three bulbs falls on the same area of the screen. The bulbs should be approximately kept at the same distance from the screen. We can put the green bulb in between the red and blue bulbs for a better result.
2. Switch on the bulbs and adjust the positions of the bulbs until you get the “whitest” light on the area of the screen and this will be the point at which the three lights mix. We can expect a better result if we make the room as dark as possible.
3. Keep a narrow opaque object like pencil, close to the screen and adjust the distance from the screen until you see three distinct colored shadows.
4. After removing the object, turn off one of the colored lights and look how the color on the screen changes. After that replace the object in front of the screen and again notice the color of the shadows. Also notice the color of the combined shadows, by moving the object close to the screen until the shadows overlap.
5. Repeat the previous step with a different light turned off while the other two remain on. Repeat again with only one colour at a time on and with different combinations. Change the size of the object and distance from the screen. You can use your hand as an object also.

### Scientific Explanation:

There are 3 receptors for coloured lights on the retina of the human eye. One type of receptor is most sensitive to red light other to green and one to blue light. We are able to perceive more than a million different shades of colour with these 3 colour receptors.

When all the 3 colours are shining on the screen, it looks white because these 3 coloured lights stimulate all the 3 colour receptors approximately equally, which will give us the sensation of white red, green and blue and therefore it is called additive primaries of light.

We can make shadows of 7 colours: blue, red, green, black, cyan (blue-green), magenta (blue-red) and yellow (red-green) by using these 3 colours.

By blocking 2 of the 3 colours, you get a shadow of the third colour. For example, we get a blue shadow while blocking red and green lights. We get a black shadow when blocking all the three lights and if you block one of the 3 lights, you get a shadow whose colour is a mixture of the other 2 colors.