Primary 5 · Science · Interactions: Magnets
Interactions: Magnets questions for Primary 5 Science
9 questions to work through online, 2 of them written out the way the paper asks. Answer and you get the working straight away, then a score at the end. No sign-up, and you can retake it as often as you like.
- Induced magnetism
- Making an electromagnet stronger
- Reading results
- Why electromagnets are useful
- Testing fairly
- Permanent and temporary
- Naming the core
- Naming what is needed
- Applying the ideas
| Turns of wire | Paper clips picked up |
|---|---|
| 20 | 4 |
| 40 | 9 |
| 60 | 13 |
| 80 | 18 |
Answers and explanations for all 9 questions
Every answer with the reasoning behind it. Worth reading after you have tried the set — or on its own, if you are a parent marking it.
A paper clip hangs from a magnet, and a second clip hangs from the first. Why does the second clip stay up?
Answer: The first clip has become a magnet while it is touching the magnet.
A magnetic material becomes a temporary magnet while it is in a magnet's field. The first clip is magnetised, so it can hold the second.
Which two of these would make an electromagnet stronger?
Answer: A and B only
More turns and more current both strengthen an electromagnet. The core has to be a magnetic material such as iron; plastic does nothing.
Based on the table above, what would 100 turns most likely pick up?
Answer: 22
Each extra 20 turns adds about 4 or 5 clips: 4, 9, 13, 18. Another 20 turns would take it to roughly 22.
Why is an electromagnet used in a scrapyard crane rather than a permanent magnet?
Answer: It can be switched off, so the load can be dropped where it is wanted.
A permanent magnet would pick the scrap up and never let go. Switching the current off releases the load exactly where the driver wants it.
The set-ups above are testing which factor?
Answer: the number of batteries
Everything matches except the batteries, so any difference in strength must come from them. That is what makes it a fair test.
Which two statements about a temporary magnet are correct?
Answer: A and B only
Soft iron magnetises easily and loses it again as soon as the field goes, which is exactly what makes it useful in electromagnets.
An electromagnet is made by winding wire around a rod. The rod must be made of a magnetic material. Which metal is normally used?
Answer: iron
The core of an electromagnet is normally iron.
An electromagnet only works while something is flowing through its coil of wire. What is flowing?
Answer: electricity
An electromagnet works only while electricity is flowing through its coil.
A recycling line uses a moving belt that passes under a strong magnet. Aluminium cans and steel cans go in together. What comes out?
Answer: The steel cans are lifted away and the aluminium cans stay on the belt.
Steel contains iron, so the magnet pulls those cans off the belt. Aluminium is not magnetic and travels on, which is how the two metals are separated.