Lesson 1 - Page 1



Can electricity make a magnetic force?


Compass, 1 or more C or D cell batteries

Bend the cardboard in the shape shown below.  Wrap about 40 turns of enameled wire around its length.  Scrap about inch of the insulation off each end.  Place the compass on the cardboard so that the needle is at right angles to the wire coil.  Connect the wire ends to the cell.  The needle will swing back and forth as it affected by the electric current.  Now add one more cell.  Note how much more the needle swings.  It proves the amount of needle movement depends on the amount of current passing through the wire.  From this fact a current meter - an ammeter can be built that will indicated how much current is flowing through a wire.  The more current, the greater the movement of the meter's needle.

Important note:  If you want to maintain the current, the cells must be connected in parallel.  That is, the negative ends and the positive ends of both cells are connected together.  If you were to connect positive to negative, you would get twice as much voltage, but the current would not increase.  Try both arrangements and see the effect on the compass needle.  Record what happens?

Now turn the compass around so the needle lies parallel to the winding.  Does the current affect the needle?

Make sure that when you are trying these experiments with a compass needle that you do not bring the compass close to a piece of iron or steel.  The needle would then swing in the direction of the metallic object and throw off your experiment.



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