Science 4th grade | UNIT 5: Electricity and magnetism 5.9 Strength of magnets
Activity 5.9 (Testing the strength of magnets)
You will need: three different magnets a metal paper clip - a ruler
Place the paper clip at the 'O' end of your ruler.
Place the north pole of magnet 1 at the other end of your ruler.
Slowly move your magnet towards the paperclip.
Stop the magnet as soon as the paperclip is attracted to and touches the magnet. Read off the distance in mm on the ruler. This is the first reading.
Now find a second reading for the north pole of magnet 1.
Now carry out the activity with the south pole of magnet 1.
Present your results in a table.
Repeat the activity to test the strength of your other two magnets.
Calculate the mean readings and fill in the mean reading column of the table. To do this you add together the first and second readings, and then divide the sum of the readings by two. For example, if the first reading is 6 mm and the second reading is 8 mm, the sum is 14 mm and the mean reading is 14 mm = 2 = 7 mm.
Draw a bar chart to present your results. Use the mean readings.
Questions
1) Were the two measurements for each magnet always the same?
2) Why is it good scientific practice to make each measurement twice?
3) Were the strengths of the north and south poles of each magnet different or the same?
4) Did the steps you followed make a fair test? Why or why not?
Challenge
Why do we need magnets that have different strengths?