Archives August 2012

YOU NEED : • A pencil that has metal on the eraser • A plastic cup with opaque sides • A small magnet   Hide a small magnet between your fingers and then turn the plastic cup upside down. With the other hand insert the eraser end of the pencil into the cup. The pencil should be placed on the side where the magnet is concealed. Now remove the hand that was holding the pencil. The pencil will continue to dangle. But you need to ensure that the magnet lies on the side of the cup where it cannot be seen. You can now remove the pencil and put the cup and the pencil on the table even as you surreptitiously remove the magnet. Those watching the trick are free top examine the cup and the pencil. They will not be able to unravel the mystery. The cup more...

YOU NEED:

• A Bulb
• Aholder
• A wooden board
• A battery

  To make an electrical switch  press two drawing i pins on a piece of wood.  Strip two wires and connect  the pins to the circuit  with a battery and a bulb.  Unfold a paper clip and hook one end  of the paper clip around one drawing pin.  Bend the other end slightly upwards and position it above the other drawing pin's head. If you press this end slightly to touch the  pin, the bulb will light up. HOW DOES IT WORK? The pin acts  as a switch.  As you would see, the purpose  of a switch is to give you the liberty of completing the circuit as and when required. When  you press  the  clip, the circuit is completed so the bulb lights up.

YOU NEED:

• One magnet
• One iron bar

You are handed over two identical iron bars A and B. You are told that one of the two is a magnet. You will not be allowed to touch any >f the bars to metal to verify, but you will have to tell  which is the magnet.   HOW DOES IT WORK?   Put the end of bar A to the middle of bar B. If there is a pull effect, A has to be the magnet or else it has to be B.

YOU NEED

• A cork
• A hard – boiled egg
• Two forks
• A bottle with a flat rimmed opening

This is  an old experiment. And the  illustration is self explanatory.   The mouth of the bottle should have a flat rim. Take the cork and cut it at the bottom so that it is concave enough  to fit on the end of the egg.   HOW DOES IT WORK?   The point  where the entire weight of an object is evenly balanced  is the centre of gravity. If you attach weights-a one kilogram and a two kilogram weight to different ends of a  broom handle then the centre of gravity would be closer  to the two kilogram weight. It will be the point where you could balance the broomstick in your hand. This explains why the centre of gravity is not necessarily at the speciall centre more...

YOU NEED :

• Some insulated copper wire
• A three inch nail
• A 9 volt battery
• Some small nails
• A piece of cardboard
• Two needles
• A bar magnet
• A cork
• A bowl of water

  Make an electromagnet by winding some insulated i pin wire all along the length of a three inch nail without overlapping the wire. Strip and connect the two ends of the  wire to the positive and negative terminals of a 9 volt battery. If you bring a few paper clips and other metallic objects close to the nail you will see that they stick to the nail and can even be picked up with it. This . happens because a magnetic force is created  from one end of the coi1 to the other end as electricity flows  through the wire. This force lines up the magnetic particles in the nail thus turning more...

YOU NEED: • A playing card   Surreptitiously, bend a card ever so lightly as shown above. The back becomes convex as in the illustration. Between the tips of your right thumb and middle finger hold the card with rear side up. Your thumb should be on corner X and the middle finger ought to be on Y. Ever so slightly ease the pressure on the corners until the cards are about to drop to the floor. While the card is almost about to fall on the floor it will also slowly turn in your hand and will be facing up. For it to rotate you will need a bit of practice to hold the card lightly. The card's movement is ghostly.  ï»¿ HOW DOES IT WORK? The convex shape raises the centre of gravity of the card. The card rotates because the centre more...

YOU  NEED

• An old Battery
• An Iron Nail
• A Fresh Lemon

  Ask an adult to carefully cut open an old torch battery, use an ordinary battery and not an alkaline one. Remove a piece of the outer casing made of zinc and  clean  it with sandpaper.  At this stage wash your hands and the zinc strip properly with soap. Dry the  strip and stick it into a soft juicy lemon.  Also insert a copper screw or nail at a distance of about 5 mm from the zinc strip. II you touch the nail and the strip lightly with the tip of the tongue  you will feel a slight tingle.   HOW DOES IT WORK? You get  the tingling sensation because the zinc and iron react with the acid in the lemon to form a simple electric cell which  produces a weak electric current.

YOU NEED

• A hammer
• A ruler
• A loop of string
• A table

  Make an odd structure and make it balance on the edge of a table. Take the length of string. Turn the string into loops so that it looks like a bracelet.   The illustration reveals how the string bracelet can hold on to the end of a ruler which in turn is attached to the end of a hammer handle. Now put the other end of the ruler on the table edge as in the illustration. You will notice the structure will stay balanced though it seems that the heavy head of the hammer will make it drop to the floor. HOW DOES IT WORK? What actually happens is that centre of gravity of the system is shifted to a point slightly under the edge of the table by the heavy head of more...

YOU NEED

• • A book
  • A piece of wooden board
  • Four pencils

  Place a book on a sloping wooden surface and push it, you will find that it moves slowly. Now place four pencils under the book, you will find it moves more easily and smoothly.   HOW DOES IT WORK? The wooden surface provides resistance to motion and slows the movement of the book. Placing four pencils under the book reduces friction and the book moves easily.

YOU  NEED :

• 18  inch length electrical wire
• A small bulb
• A holder
• Battery

  Connect two 18 inch lengths of electrical wire to the connectors of a bulb holder. Set a small bulb in the holder. Connect the other ends of the wires to the terminal of a battery with clips. As you complete the connections, the bulb will light up because the circuit is complete.   HOW DOES IT WORK? Current flows from the positive terminal of the battery towards the bulb.  Inside the bulb it flows through the filament towards the negative terminal of the battery. Since the path is not broken, the circuit is complete and the bulb lights up.