How LDR Works ???

By thinknut.blogspot.com

How LDR Works ???

 

     
     LDRs or Light Dependent Resistors are very useful especially in light/dark sensor circuits. Normally the resistance of an LDR is very high, sometimes as high as 1000 000 ohms, but when they are illuminated with light resistance drops dramatically.

OR

    An LDR is a component that has a resistance that changes with the light intensity that falls upon it. They have a resistance that falls with an increase in the light intensity falling upon the device.

Symbol :

Working :

The resistance of an LDR may typically have the following resistances.

Daylight	= 5000 ohms
Dark	= 20000000 ohms

You can therefore see that there is a large variation between these figures. If you plotted this variation on a graph you would get something similar to that shown by the graph to the right.

The animation opposite shows that when the torch is turned on, the resistance of the LDR falls, allowing current to pass through it.

Circuit Wizard software has been used to display, the range of values of a ORP12, LDR . When a light level of 1000 lux (bright light) is directed towards it, the resistance is 400R (ohms). When a light level of 10 lux (very low light level) is directed towards it, the resistance has risen dramatically to 10.43M (10430000 ohms). This is an example of a light sensor circuit : When the light level is low the resistance of the LDR is high. This prevents current from flowing to the base of the transistors. Consequently the LED does not light. However, when light shines onto the LDR its resistance falls and current flows into the base of the first transistor and then the second transistor. The LED lights. The preset resistor can be turned up or down to increase or decrease resistance, in this way it can make the circuit more or less sensitive.

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By thinknut.blogspot.com

Magic ink

Help your kids discover the magic of the amazing science experiment and kids activity that creates magic ink. Watch their eyes widen in wonder as they uncover the secrets behind the amazing possibilities of science!

Number of players:

1+

What you need:

• lemon
• water
• small plate
• toothpick
• white paper
• lamp

Activity:

Squeeze the lemon juice into a small plate with a few drops of water and mix with a spoon.

Dip the toothpick into the lemon juice mix and write a message on the white sheet of paper.

When it dries the writing will be invisible.

Heat the paper by holding it over a lamp with the writing side down.

The invisable ink writing will slowly turn brown and appear on the page!

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how to Make a candle experiment

By thinknut.blogspot.com

Make a candle experiment

 

 

Science experiments are so much fun for kids and so easy to do in your own home. Teach the kids how to make a candle with this cool experiment which explains how the process works. Once it's finished, you can then burn your own home made candle!

Number of players:

1+

What you need:

• pieces of white candles
• wax crayons
• pan
• string
• skewer
• paper cup

Activity:

Put the candles and the wax crayons into a pan.

Ask an adult to melt them slowly over low heat.

Stir gently to mix together.

While the wax is melting, make a small hole in the bottom of the cup with a skewer.

Thread a piece of string through it.

Tie a knot underneath it.

Ask an adult to pour the wax into the cup with the piece of string dangling outside it.

Hang your wax candle up by the piece of string to dry. The wax will turn hard.
Why?
Wax can change from a solid to a liquid when it is heated.

It will become solid again when it cools.

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Candle Science Magic

By thinknut.blogspot.com

You know you can put out a candle flame by pouring water on it. In this science magic trick or demonstration, the candle will go out when you pour 'air' onto it.

Blow out a candle by pouring a glass of what appears to be air onto the flame. This easy science trick demonstrates what happens when air is replaced with carbon dioxide.

Candle Science Magic Trick Materials

• a lit candle
• a transparent glass (so people can see what is inside the glass)
• baking soda (sodium bicarbonate)
• vinegar (weak acetic acid)

Set up the Magic Trick

In the glass, mix together a little baking soda and vinegar.

How to Blow Out the Candle with Chemistry

Simply pour the gas from the glass onto the candle. The flame will be extinguished. Another way to perform this trick is to pour the gas that you just made into an empty glass and then pour the apparently empty glass over the candle flame.

How the Candle Trick Works

When you mix baking soda and vinegar together, you produce carbon dioxide. The carbon dioxide is heavier than air, so it will sit in the bottom of the glass. When you pour the gas from glass onto the candle, you are pouring out the carbon dioxide, which will sink and replace the (oxygen-containing) air surrounding the candle with carbon dioxide. This suffocates the flame and it goes out.

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How make hot ice

By thinknut.blogspot.com

How to make hot ice

All you need are two common kitchen ingredients to make hot ice - a non-toxic chemical that crystallizes when you touch it into a material that looks like ice except it gives off heat. See how to make hot ice and get ideas for fun hot ice activities.

You Will Need :

• White Vinegar
• Backing Soda

Process :

          Mix one liter of vinegar with 4 tablespoons of baking soda. These chemicals react to form nontoxic sodium acetate or hot ice in water. You need to boil off most of the water, so heat the solution until it is boiling and keep applying low heat until you see a crystal skin start to form on the surface of the liquid. Remove the hot ice solution from heat, pour it into a new container and refrigerate the solution until it is chilled.

          When the hot ice has cooled, you can get it to instantly crystallize simply by touching it. You can try crystallizing the hot ice as you pour it, too. Either way, the solution will give off heat as it crystallizes.

          You can re-dissolve and reheat the hot ice to play with it again or you can throw it away when you are finished. 

          I hope you've enjoyed making hot ice.

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How Acids and Bases Produce Colors!

By thinknut.blogspot.com

Watch Acids and Bases Produce Colors!

Show your child how to create a concoction of simple household ingredients that changes colors as acids and bases are added! This magic mixture is called a "pH indicator," a chemical compound that is added to a solution in order to visually determine its acidity or basicity. While many items (such as cabbage juice) have this ability, this mixture of turmeric and rubbing alcohol possesses the unique trait of being able to change BACK to its original color. Science has never been this fun!

What You Need:

• Bowl
• 1/4 cup water
• 1/4 cup vinegar
• 1/2 teaspoon turmeric
• 1/2 cup rubbing alcohol
• 1 teaspoon baking soda
• Clear drinking glass

What You Do:

1. Have your child combine the turmeric and rubbing alcohol in the bowl.
2. Combine the baking soda and water in the glass.
3. Help your child to pour a sufficient amount of the turmeric/alcohol combination into the glass to effect a color change. Ask her to observe the reaction. What color was produced?
4. Have your child pour the vinegar into the glass.

What's Going On? Adding the pH indicator to the basic solution should have turned it red. Adding an acid (vinegar) made it foam and revert to its original yellow color.

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Experiment with Salt Water Conductivity

By thinknut.blogspot.com

Experiment with Salt Water Conductivity  

   

    
Does your child know that salt water conducts electricity? In this science experiment, your child will build a mini circuit to find out if she has salt water or fresh water. It's a simple experiment but it will show how saltwater acts as a conductor to electrical currents, while reinforcing important lessons about conductivity and electricity.

What You Need:

• Masking tape
• 9-volt battery
• Buzzer (can be bought at an electronics store such as Radio Shack)
• 2 craft sticks
• Aluminum foil
• Water
• Salt water

What You Do:

1. First, cover both craft sticks with aluminum foil.
2. Take your buzzer and tape the red wire to the positive end of the battery (the + sign).
3. Tape one foil covered craft stick to the black wire. Tape the other one to the negative side of the battery (- sign).
4. Test you buzzer by touching the two sticks together. This should make the buzzer sound. If it doesn’t work, make sure that everything is taped together in the right way.
5. Now put the tips of the metal sticks in the salt water about an inch apart. Make sure the two sticks don’t touch. The salt water will act like a wire connecting the metal sticks and completing the circuit which will make the buzzer go off!
6. Try the experiment in the fresh water. Why does your child think that the buzzer sounded in the salt water but not the fresh water?

What Happened? The salt dissolves into the water and breaks down into "ions". which act as a conductor. Fresh water does not have these ions, therefore it cannot conduct the electrical current

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Homemade solar cell construction

 

              By thinknut.blogspot.com

Homemade solar cell construction

• 
  

                  

A solar cell or photovoltaic cell is an electrical device that converts the light energy  into electricity by the photovoltaic effect. solar cell basic unit of solar panel and construct at industrial level you can not build at home but in this article we will try to teach you simple homemade solar cell construction in Urdu. this solar cell is not efficient like industrial cell but it can convert less amount of sunlight in electric.

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How to make Exploring Soil Sandwiches

                                 

                                                       By thinknut.blogspot.com

Exploring Soil Sandwiches

                

The soil beneath your feet all looks the same, doesn’t it? Surprisingly, soils in different locations actually have different components. In this science project, you can examine the layers that make up various soil samples and think about why the samples are so different from each other.
All soils are made of four components: clay, loam, sand, and silt. This science project identifies the differences between soils from different environments and attempts to figure out why those differences exist.

Problem:

How does soil from various locations differ?

Materials:

• Soil from various locations
• Trowel
• Several glass jars
• Masking tape and marker (for labeling)
• Water
• Turkey baster
• Magnifying glass

Procedure:

1. Identify at least three sites that you think might have different types of soil, such as a playground, a backyard garden, a riverbed, and a wooded area. These sites should all be public property in which is not forbidden to dig (or your own personal property).
2. Hypothesize how the soil from these locations might differ from one another.
3. Dig up some of the soil from one location, and fill a jar with about two inches worth of the soil. Label the jar with a description of the location.
4. Write down some of the plant and animal life you see around the location.
5. Repeat this process with each of the other sites you chose.
6. Fill each jar to the top with water. Twist each lid on tightly, and shake vigorously for thirty seconds.
7. Leave the jars for about an hour, making sure that all of the soil has completely settled. Check on the jars every fifteen minutes or and take data on what each jar looks like each time you check. Which soil sample settled first? Last?
8. Take the lid off each jar. Squeeze the bulb of the baster and insert it into the first jar. Release the bulb to suction the water into the baster, and discard the water. Repeat this process several times which each jar until you have removed as much water as possible.
9. Look at each sample under a magnifying glass. Draw a diagram of each soil sample, pointing out each layer of soil (clay, loam, sand, and silt) and anything else that differentiates between the samples.
10. Consider why you found these differences, and how they could be related to the conditions surrounding each location.

Keren Perles has worked as an educational writer, editor, teacher, and tutor of all ages. Her experience spans the subject areas, from science and math, to English and the Hebrew language.

Disclaimer and Safety Precautions

thinknut.blogspot.com provides the Science Fair Project Ideas for informational purposes only. thinknut.blogspot.com does not make any guarantee or representation regarding the Science Fair Project Ideas and is not responsible or liable for any loss or damage, directly or indirectly, caused by your use of such information. By accessing the Science Fair Project Ideas, you waive and renounce any claims against thinknut.blogspot.com that arise thereof. In addition, your access to thinknut.blogspot.com  website and Science Fair Project Ideas is covered by thinknut.blogspot.com Privacy Policy and site Terms of Use, which include limitations on thinknut.blogspot.com’s liability.

Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.

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Mirror Experiment

                                

                                                       By thinknut.blogspot.com

Plane Mirror Reflection Experiment

                

Plane (flat) mirrors have a reflective surface that bounces back light within 180 degrees of the mirror's face. We use these mirrors every day in our bathrooms, bedrooms, and cars. When you look in a plane mirror, you see a mirror image that is flipped backwards and opposite to the objects it is reflecting.
You’ve been tasked with projecting a line of text onto a glass screen for a magic show. However, the projector can’t be on stage, and is instead around a corner, and it’s too bright for the trick. You only have two mirrors. How can you project an image of the text on the glass screen that is dim but readable? Let’s do a mirror physics experiment and see if you can use what you learn to think of a clever solution!

Problem:

How does the angle of two mirrors change the reflection of an object?

Materials

• Protractor
• Two identical, small plane mirrors
• Modeling clay
• Small object (coin, small figure, etc.)
• Strip of paper
• Pen
• Plastic packing tape

Procedure

1. Tape your mirrors together so that they can be opened and closed like a hinge. You want to leave a slight gap between the two edges (around 1/16th of an inch) to do this.
2. Mark angles of 30, 36, 45, 60, 90, 120 and 180 degrees on a piece of paper using your protractor.
3. Place the hinge of your mirrors at the vertex of your marked angles.
4. The first angle you will test will be 180 degrees.
5. Place your object (you can embed it in modeling clay if it won’t stand up on its own) in the middle of the mirrors and look at the reflection. How many objects do you see, including both reflected and real?
6. Keeping the object equally between the two mirrors, move the mirrors together into the other angles you marked out with your protractor. How many objects do you see at each angle? Is there something about the angle can help you predict how many objects you will see? Is every reflected image the same brightness?
7. Write a word on a piece of paper, and place it in between the mirrors at 60 degrees. Look closely at the second reflection (the reflection of the reflection). Can you read the text? Why do you think this is happening?

Results

You will see an ever-increasing number of objects as you move the mirrors closer together (reducing the angle between them). Whenever you can see a whole number of images reflected, the angle of the mirrors will perfectly divide into 360 degrees. When you look at the reflection of a reflection you will be able to read the text in the mirror, as if you pointed a camera at the object. The reflections should get dimmer (more silvery) as the number of times they are reflected increases

Why?

The mirrors reflect the reflections of other mirrors within 180 degrees of the mirror’s face. When mirrors reflect, the reflected image will be backwards, but if you reflect something twice, it will look normal.
Because light is traveling in a straight line to and from each mirror, the light will bounce a number of times back and forth between the mirrors before it travels from the object to your eye. The number of times the light bounces (and the number of objects that you see) will correlate to the number of times the angle divides into 360. As the mirrors get closer and closer to having zero angle between them, more and more images appear. At an angle of 0 degrees, or when the two mirrors are facing each other, there are an infinite number of reflections.
So, how are you going to accomplish your trick? You can make the text appear by lining up your mirrors and your projector so that the light bounces an even number of times before it gets to your eyes. Using multiple mirrors will also dim the image before it hits the glass plate for the trick.

Disclaimer and Safety Precautions

thinknut.blogspot.com provides the Science Fair Project Ideas for informational purposes only. thinknut.blogspot.com does not make any guarantee or representation regarding the Science Fair Project Ideas and is not responsible or liable for any loss or damage, directly or indirectly, caused by your use of such information. By accessing the Science Fair Project Ideas, you waive and renounce any claims against thinknut.blogspot.com that arise thereof. In addition, your access to thinknut.blogspot.com website and Science Fair Project Ideas  thinknut.blogspot.com Privacy Policy and site Terms of Use, which include limitations on liability.

Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.

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