Year 7 Science · Unit 3 · Lesson 15
Challenge Worksheet
Learning Goals
Read the results
Investigation data
A group built an electromagnet using an iron nail and a single 1.5 V cell. They counted how many paper clips the tip could pick up for different numbers of turns of wire. They kept the same nail, the same cell and the same paper clips each time.
| Number of turns | Paper clips picked up |
|---|---|
| 10 turns | 2 |
| 20 turns | 5 |
| 30 turns | 7 |
| 40 turns | 10 |
Describe the pattern in the results, then explain the science behind it. Predict roughly how many paper clips 50 turns might pick up, and explain why this counts as a fair test. Use scientific terms (electromagnet, turns, current, magnetic field, fair test) in your answer.
1. A different group claims their electromagnet got stronger when they added more turns. But each time they also swapped to a fresh, fuller battery. Explain why their conclusion is not reliable, and describe how they should change their method to fix it.
2. An engineer needs a magnet for a machine that must grip steel parts firmly but also release them quickly and often. Would you recommend a permanent magnet or an electromagnet? Justify your choice and explain one way the engineer could make the magnet strong enough for heavy steel parts.
Wrap Up
In one sentence, what was the main idea of this lesson?