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Electromagnet


A homemade electromagnet that consist of a bolt and wire coiled around it will pick up a collection of small nails. Larger professional electromagnets are available on request.

Parts: electromagnet, power supply, small nails

Simple Electroscope



Materials:


Background:

An electroscope is an instrument for detecting the presence of static electricity. It consists of two thin metal leaves suspended from a metal hook. When the hook is brought near a source of static electricity, some of the electrons in the hook are pushed to the leaves (if the source is negative) or pulled up to the hook from the leaves (if the source is positive). Either way, the leaves are now charged the same way as each other and so they repel each other. The amount they open up is proportional to the charge of the source (if the sources are always held at the same distance from the hook).

Procedure:

Cut two strips of foil lcm by 4cm (1/3" by 1 1/2") Open out the paperclip to form the shape at right. Push the hook through the middle of the index card and tape so that it is at right angles to the card. Lay the two foil strips on top of one another and hang them on the hook by pushing the hook through them. Lay the card over the jar so that the strips hang inside (see picture below).

Bring various charged objects near the hook and observe what happens. Notice what happens to the strips when the sources are removed. Does anything different happen if the source actually touches the hook? If the strips do not fall back together, gently touch the hook with your finger.



Demonstration for Newton's Second and Third Laws

NEWTON'S CART

If you would like to try a more sophisticated experiment that demonstrates Newton's Laws of Motion build a Newton Cart. In this experiment a wooden block is thrown by a slingshot-like device from a cart and produces a thrust that causes the cart to move in the opposite direction.

Materials:

Background:

Procedure:
  1. Screw the three screws in the large wood block as shown in the figure.
  2. Drill a hole through the bottom of the plastic cup into the center of the smaller wood block.
  3. Use the No. 8 screw with washer and attach the cup to the small wood block.
  4. Lightly wax and polish the bottom of the small wood block.
  5. Tie several loops of string the same size.
  6. Place one string loop over a rubber band and then place the ends of the rubber band over the two screws on one end of the large wooden block.
  7. Pull the rubber band back like a slingshot and slip the string over the third screw to hold the rubber band stretched.
  8. Arrange the pencils or dowel rods in a row like railroad ties on a level table top. Set the large block on one end of the row so that the single screw points to the middle of the row. Slip the small block (without any pennies in the cup) into the rubber band.
  9. Light a match (get a parent to help with this step) and ignite the ends of the string hanging down from the loop. When the string burns through, the rubber band will throw the block off the cart and the cart will roll in the other direction. Note how far the cart travels along the floor or table top.
  10. Reset the equipment and add a second rubber band. Again, light the string and note how far the cart travels.
  11. Reset the equipment again with 3 rubber bands. Try again with one rubber band and all the pennies of one roll. Repeat this procedure systematically varying the number of rubber bands and the number of pennies in the cup. Record how far the cart travels under each condition tested. Note any trends. You should find correlation's with the amount of force (determined by number of rubber bands) and the amount of mass displaced ( determined by number of rolls of pennies placed in the cup. You may even want to make measurements and graph your data.

Email: e071689@orca.cc.metu.edu.tr