204 Simple Science Experiments ~ {ERG}

[LoneRanger]



31. Mini-microphone

[b]Push two pencil leads through the short sides of a matchbox, just above the base. Scrape off some of the surface, and do the same with a shorter lead, which you lay across the top. Connect the microphone with a battery and earphone in the next room. (You can take the earphone from a transistor radio.) Hold the box horizontal and speak into it. Your words can be heard clearly in the earphone.

The current flows through the graphite

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32. Mysterious Circles



Push a length of copper wire through a piece of cardboard laid horizontally and connect the ends of the wire to a battery. Scatter iron filings on to the cardboard and tap it lightly with your finger. The iron filings form circles round the wire. If a direct current is passed through a wire or another conductor, a magnetic field is produced round it. The experiment would not work with an alternating current, in which the direction of the current changes in rapid sequence, because the magnetic field would also be changing continuously.

[LoneRanger]



33. Electro- magnet

Wind one to two yards of thin insulated wire on to an iron bolt and connect the bare ends of the wire to a battery. The bolt will attract all sorts of metal objects.

The current produces a field of force in the coil. The tiny magnet particles in the iron become arranged in an orderly manner, so that the iron has a magnetic north and South Pole. If the bolt is made of soft iron, it loses its magnetism when the current is switched off, but if it is made of steel it retains it.

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Electro Buzzer

(Please See Image Above)

Nail board B and wooden blocks C and D onto board A (about 5 X 5 inches). Push an iron bolt F through a hole bored in B. Wind covered copper wire G 100 times round the bolt and connects the ends to a battery and to H respectively. Bore a hole through block C and wedge the fret saw blade H firmly into it so that its end is a short distance from bolt F. Hammer a long nail K through A and bend it so that its point rests in the middle of the saw blade. Oil the point of the nail. Use a piece of beading E as a key, with a rubber band P as spring and drawing pins M and N as contacts. Join all the parts with connecting wire (remove the insulation).

If you press the key down, you connect the electric circuit, bolt F becomes magnetic and attracts H. At this moment the circuit is broken at K and the bolt loses its magnetism. H jumps back and reconnects the current. This process is repeated so quickly that the saw blade vibrates and produces a loud buzz. If you wish to do Morse signaling with two pieces of apparatus, you must use three leads as in the lower circuit diagram.

[LoneRanger]



35. Light fan

Hold a light-coloured rod between your thumb and forefinger and move it quickly up and down in neon light. You do not see, as you might expect, a blurred, bright surface, but a fan with light and dark ribs.

Neon tubes contain a gas, which flashes on and off 50 times a second because of short breaks in alternating current. The moving rod is thrown alternatively into light and darkness in rapid sequence, so that it seems to move by jerks in a semicircle. Normally the eye is too slow to notice these breaks in illumination clearly. In an electric light bulb the metal filament goes on glowing during the short breaks in current.

[LoneRanger]



36. Clinging balloons

Blow up some balloons, tie them up and rub them for a short time on a woollen pullover. If you put them on the ceiling, they will remain there for hours.

The balloons become electrically charged when they are rubbed, that is, they remove minute, negatively charged particles, and called electrons, from the pullover. Because electrically charged bodies attract those, which are uncharged, the balloons cling to the ceiling until the charges gradually become equal. This generally takes hours in a dry atmosphere because the electrons only flow slowly into the ceiling, which is a poor conductor.

[LoneRanger]



37. Pepper and salt

Scatter some coarse salt onto the table and mix it with some ground pepper. How are you going to separate them again?

Rub a plastic spoon with a woollen cloth and hold it over the mixture. The pepper jumps up to the spoon and remains sticking to it. The plastic spoon becomes electrically charged when it is rubbed and attracts the mixture. if you do not hold the spoon too low, the pepper rises first because it is lighter than the salt. To catch the salt grains, you must hold the spoon lower.

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38. Coiled Adder

Cut a spiral-shaped coil from a piece of tissue paper about 4 inches square, lay it on a tin lid and bend its head up. Rub a fountain pen vigorously with a woolen cloth and hold it over the coil. It rises like a living snake and reaches upwards.

In this case the fountain pen has taken electrons from the woolen cloth and attracts the uncharged paper. On contact, the paper takes part of the electricity, but gives it up immediately to the lid, which is a good conductor. Since the paper is now uncharged again, it is again attracted, until the fountain pen has lost its charge.

[LoneRanger]



39. Water bow

Once more rub a plastic spoon with a woollen cloth. Turn the water tap on gently and hold the spoon near the fine jet. At this point, the jet will be pulled towards the spoon in a bow.

The electric charge attracts the uncharged water particles. However, if the water touches the spoon, the spell is broken. Water conducts electricity and draws the charge from the spoon. Tiny water particles suspended in the air also take up electricity.

Therefore experiments with static electricity always work best on clear days and in centrally heated rooms.

[LoneRanger]



40. Hostile balloons

Blow two balloons right up and join them with string. Rub both on a woolen pullover and let them hang downwards from the string. They are not attracted, as you might expect, but float away from each other.

Both balloons have become negatively charged on rubbing because they have taken electrons from the pullover, which has now gained a positive charge. Negative and positive charges attract each other, so the balloons will stick to the pullover. Similar charges, however, repel one another, so the balloons try hard to get away from each other.

[LoneRanger]

41. Shooting puffed rice

Charge a plastic spoon with a woolen cloth and hold it over a dish containing puffed rice. The grains jump up and remain hanging on the spoon until suddenly they shoot wildly in all directions.

The puffed rice grains are attracted to the electrically charged spoon and cling to it for a time. Some of the electrons pass from the spoon into the puffed rice, until the grains and the spoon have the same charge. Since, however, like charges repel one another, we have this unusual drama.

[LoneRanger]

42. Simple Electroscope

Bore a hole through the lid of a jam jar and push a piece of copper wire bent into a hook through it. Hang a folded strip of silver paper, from which you have removed the paper, over the back. If you hold a fountain pen, comb, or similar object, which has been electrically charged by rubbing on the top of the wire, the ends of the strip spring apart.

On contact with a charged object, electrical charges flow through the wire to the ends of the strip. Both now have the same charge and repel one another according to the strength of the charge.

[LoneRanger]

43. Electrical ball game

Fix a piece of silver paper cut into the shape of a footballer on to the edge of a phonograph record, rub the record vigorously with a woolen cloth and place it on a dry glass. Put a tin can about two inches in front of the figure. If you hold a small silver-paper ball on a thread between them, it swings repeatedly from the figure to the can and back.

The electric charge on the record flows into the silver-paper figure and attracts the ball, it becomes charged, but is immediately repelled because the charges become equal, and goes to the can, where it loses its electricity. This process is repeated for a time.

[LoneRanger]



44. Electric fleas

Rub a long-playing record with a woolen cloth and place it on a glass. If you toss some small silver-paper balls on to the record, they will jump away from one another in a zigzag motion.

If you then move the balls together with your fingers, they will hop fiercely away again.

The electricity produced on the record by rubbing is distributed in irregular fields. The balls take up the charge and are repelled, but are again attracted to fields with the opposite charge. They will also be repelled when they meet balls with the same charge.

[LoneRanger]



45. Puppet dance

Lay a pane of glass across two books, with a metal plate underneath. Cut out dolls an inch or so high from tissue paper. If you rub the glass with a woollen cloth, the dolls underneath begin a lively dance. They stand up, turn round in a circle, fall, and spring up again.

The glass becomes electrically charged when it is rubbed with the wool, attracts the dolls, and also charges them. Since the two like charges repel each other, the dolls fall back on the plate, give up their charge to the metal and are again attracted to the glass.