1. Place a compass on the table. Wait until the needle stops moving. Bring a small magnet near the compass.
 a) Record your observations.
2. Move the magnet around slowly.
a) What happens to the compass?
3. Create a code so that someone looking at the compass can read the code. The person reading the code can manipulate the compass from under a piece of paper.
a) How fast can you send the code?
4. Remove the magnet. Place a wire on top of the compass, as shown. Briefly touch the ends of the wire to the ends of the battery.
a) What happens to the compass needle?
 5. Create a setup where the wire is placed on the compass and the presence of a current creates a code. The code can then be read by observation of the compass.
a) How fast can you send this code?
b) Does this code have any advantages over the code in step 3?
6. Turn the wire to a different direction and repeat step 4.
a) What happens this time? Try several different directions.
7. Obtain a 5-m length of wire and a cardboard tube. Carefully strip 1 cm of insulation from each end of the wire. Wrap the wire around the cardboard tube, with all turns going in the same direction. Before you start, leave about 30 cm on each end for making connections. Tape the coil of wire in place.
8. Connect the ends of the wire to a meter that measures small currents. This type of meter is called a galvanometer.
 10. Create a code that can be read by someone observing the current meter in step 8.
a) How fast can you send this code?
b) Does this code have any advantage over the codes used in steps 3 and 5?
11. Make electromagnets by wrapping wire around nails. Be sure the last few centimeters of insulation is sanded off each end of each wire. You will investigate the effect of the number of turns of wire. Wind each piece of wire tightly around a separate nail. For each nail, wind a different number of turns. Leave enough unwrapped wire at each end to connect to a cell. Tape each coil of wire in place.
12. Hook up one coil to a battery as shown in the drawing. Figure out a way to measure the strength of your electromagnet. Hint: You can count how many paper clips or washers the electromagnet will pick up. Leave the battery connected for as short a time as possible to limit the battery's energy loss.
13. Connect several batteries together end-to-end, as in a flashlight. Make an electromagnet with these batteries.
a) How does using several batteries change the strength of your electromagnet?
14. A digital code is a set of ones and zeroes. An analog code is a continuous set of numbers, like the number line in mathematics, between zero and one.
a) Which of the methods you investigated in this activity can be used for digital coding?
b) Which of the methods you investigated in this activity can be used for analog coding?
c) Which of the methods can be used for both?
d) What advantage would digital coding have over analog coding?
e) What advantage would analog coding have over digital coding? |
