Procedure: PART A. North meets south 1. Checking Polarity. Place one magnetic compass on a horizontal surface. Then, move a bar magnet around and above it exploring the strength and polarities of the magnet. If a cellular phone or any gadget with built in camera is available, take pictures of the magnetic compass needle orientations for different locations around the bar magnet. Draw the compass needle directions and write your observations regarding the magnetic field strength on your science notebook and answer the guide questions. Guide Questions: Q16. What happens when you randomly move the bar magnet roundabout and above the compass one foot or farther? Nearer than a foot? Q17. Compass needles are tiny magnets that are free to indicate the north and south poles of a magnet? What do you need to do to know the magnet’s polarities? Q18. What does the compass needles indicate about the iron nail shown below in Figure 6? Figure 6. Use of Compass Needles for Checking the Magnetism PART B. By the touch of a magnet 1. Magnetization by stroking. Pour iron filings on a sheet of paper and check whether the filings are still non-magnetized. If magnetized, stir or move the iron filings gently on the paper. 2. Fill carefully the narrow test tube up to a quarter with these iron filings. Cover with masking tape or cork
98 3. Hold the closed test tube horizontally. Shake or roll gently with your fingers to level out the iron filings inside. Figure 7a. Leveling the Iron Filings inside the Test Tube 4. Then when levelled, touch with the north-pole end of the permanent magnet the test tube’s curved end. Move the magnet along the test tube from this end to the covered end. Lift the magnet off the test tube and repeat with ten or more strokes. On your science notebook, observe and record what happens inside the tube. 5. Gently lay the test tube on a table and bring compasses near both ends of the test tube as shown in Figure 7.b below. Observe and record what happens. Figure 7b. Testing Induced Magnetism on the Iron Filings 6. Carefully shake the test tube as shown in Figure 7.c, without moving the compasses. Test for the presence of magnetism again. Record your observations. Figure 7c. Shaking the Iron Filings inside the Test Tube Guide Questions: Q19. In step no. 4 are the iron filings in the test tube magnetized? If yes, which end is the north and which is the south? If no, what else can be done to magnetize it? Try and record your idea. Q20. What happened to the iron filings magnetism after several shakes?