The method and the results are on the electromagnet lab. Do the analysis yourself first, then check the answers below.
Quick answer: A magnet has a north and a south pole: like poles repel and unlike poles attract. These answers go with the grade 8 science lab on electromagnet: the graph, the calculations, the uncertainties and the conclusion explained, for all 7 analysis questions.
Model answers use the sample table. Your own counts will differ a little, but you should still find that the number of clips rises steadily with the turns, giving a line close to a straight line through the origin.
The points lie close to a straight line through the origin, so the clips are proportional to the turns. Gradient = (16.3 − 3.3) ÷ (50 − 10) = 13 ÷ 40 = 0.33 clips per turn.
Question 4 Prediction
35 turns: 0.325 × 35 = 11.4, so about 11 clips. 60 turns: 0.325 × 60 = 19.5, about 20 clips. The 60-turn value is less reliable because it is outside the range tested.
Question 5 Explain the trend
Each turn of wire carries the same current and makes its own magnetic field. The fields of all the turns add together, so the nail becomes a stronger magnet and attracts more clips.
Question 6 Reliability
Repeating shows how much the results vary, and a mean reduces the effect of random errors. A reading far from the rest is an anomaly: check it, repeat it, and leave it out of the mean if it is clearly a mistake.
Question 7 Improvements
The cells run down as the current flows, so switch on briefly and check the voltage; also use small steel washers or weigh the load lifted to get a finer measure than whole paper clips. Any two sensible improvements.
