Activity Page 3

Reflecting on the Activity and the Challenge

You have investigated a relationship between magnetism and electricity. A magnet affects a compass as does an electric current. You have also created electricity by moving a magnet past a coil of wire. Finally, you have made an electromagnet by using current to create the magnet. Each of these mechanisms was then used by you to code a message. Some of these approaches were limited to digital codes while others could be digital or analog codes.

In setting up your communication system for the chapter challenge, you may decide to use one of these techniques. You will have to decide whether your code should be digital or analog. You may also view one of these methods as a way to prevent a message from being transmitted. This may be important in maintaining secrecy in the second part of your challenge.

Physics To Go

1.

a) If you place a compass on the table, which way does the compass needle point?

b) What happened to the compass needle when an electric current ran through the wire?

c) Does the current in the wire make the compass point in a particular direction? Can you identify that direction?

d) In step 6, you turned the wire in many different directions. Was there one direction where the electric current did not change the compass? Provide an explanation for this.

e) In step 12 you connected together several batteries end-to-end and investigated their effect on the electromagnet. Predict what would have happened if you had done that in the activity with the wire and the compass.

2.

a) Make a drawing to show a compass under a wire.

b) Draw the compass when the wires are connected to a battery.

c) Draw the compass when the wires in part (b) are reversed.

3.

a) In this activity, you made a coil to investigate how a moving magnet can produce electric current. What would have happened if you had just used a straight wire?

b) In step 3, you ran a current through a straight wire to investigate the effect on a compass. Predict what would have happened if you had used a much longer wire and wound it into a coil.

4.

Predict what would happen if you brought the compass near the electromagnet.

5.

a) List the variables that affect the strength of an electromagnet.

b) Briefly, tell how you would investigate each variable.

6.

Review the steps in this activity where you used a coil of wire. What effect did the coil of wire have in each case?

7.

a) Locate the circuit breaker box or fuse box in your home.

b) With the help of an adult, find out how the switches, fuses, or breakers work.

8.

a) Sketch your electric meter, including the readings on the dials and the positions of the hands. Date your sketch.

b) One week later, sketch the meter and the readings again.

c) Figure out how much electricity you used in that week.

Stretching Exercises

1. Investigate the effect of wrapping a coil around a compass and running current through the coil. Find out the effect of changing the number of turns in the coil. Also find out the effect of adding a second coil with the same number of turns as the first.

2. Build a compass by magnetizing a paper clip and floating it on water. Find out what happens when you bring a coil of wire near the compass and using a battery run current through the coil.

3. Investigate how an electromagnet affects a compass. Also, investigate how two electromagnets affect each other, and how two compasses affect each other. Write a summary of everything you have discovered.