Year 7 Science · Unit 3 · Lesson 15
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Each word is used at most once. Two words are not needed: cross them out.
A magnetic is the region around a magnet where its force acts. Outside a magnet, field lines point from the pole to the pole. You can map a magnetic field by sprinkling iron on paper over a magnet. An electromagnet is made by passing an electric through a coil of wire. Adding an core inside the coil makes the electromagnet much stronger.
Match each word to its meaning
Write the letter of the correct meaning next to each word. Each letter is used once.
| Word | Letter | Meaning |
|---|---|---|
| Magnetic field | A. A coil of wire that makes a magnetic field when current flows through it | |
| Field line | B. The region around a magnet where its force acts on magnetic materials or other magnets | |
| Solenoid | C. A piece of iron, such as a nail, inside a coil that makes an electromagnet much stronger | |
| Electromagnet | D. A line drawn to show the shape and direction of a magnetic field | |
| Iron core | E. A temporary magnet made by passing an electric current through a coil of wire |
Sort it: what does each change do?
Leo’s coil is wound round a nail and connected to a single cell. Sort the changes below into the boxes. The boxes do not hold the same number of items.
Makes it stronger
Makes it weaker
Switches it off
1. Draw a bar magnet with at least four field lines around it. Label the N and S poles, add an arrow to each line, and draw the lines closest together where the field is strongest.
Read the data: what should go inside the coil?
Scenario: testing cores
Ella wound 30 turns of insulated wire around a drinking straw and joined it to one cell. She slid a different rod into the straw each time, or left it empty, and counted the steel paper clips it lifted.
| Rod inside the coil | Paper clips lifted |
|---|---|
| nothing (empty straw) | 1 |
| iron nail | 8 |
| copper rod | 1 |
| wooden skewer | 1 |
| plastic pen tube | 1 |
Source: sample class results.
2. Which rod made the electromagnet strongest? How many times more clips did it lift than the empty coil?
3. The copper, wooden and plastic rods gave the same result as an empty coil. Explain why, and why the iron nail was different.
4. A student’s drawing shows two field lines crossing near a strong magnet. Explain why the drawing must be wrong.
5. Leo builds a simple electromagnet. Describe what he needs and how he puts it together, and give one safety rule. Then explain why his electromagnet can be switched off, but a fridge magnet cannot.
Fill the gap
field; north; south; filings; current; iron. Not used: heavier, colour.
Match each word to its meaning
Magnetic field → B; Field line → D; Solenoid → A; Electromagnet → E; Iron core → C.
Sort it: what does each change do?
Stronger: more turns; a second cell (more current). Weaker: nail out; fewer turns. Off: disconnecting the cell.
Question 1
At least four smooth, curved lines from one pole round to the other, not crossing, with N and S labelled (1). Arrows point away from N and towards S outside the magnet (1). Lines drawn closest together at the poles (1). [3 marks]
Question 2
The iron nail (1). 8 ÷ 1 = 8 times as many clips (1). [2 marks]
Question 3
Copper, wood and plastic are not magnetic materials, so they add nothing to the coil’s field (1). Iron is a magnetic material: the coil’s field makes the nail magnetic, and its field adds to the coil’s (1). [2 marks]
Question 4
Field lines never cross, however strong the field (1). A compass at a crossing point would have to point in two directions at once, and it can only point one way (1). [2 marks]
Question 5
Marking guide, 1 mark each: insulated wire, an iron nail and a low-voltage cell; wind the wire into a coil round the nail and join its ends to the cell; safety: use only a low-voltage cell, never mains, or disconnect between tests because the wire gets warm; the magnetism comes from the current flowing in the coil; when the current stops the magnetism disappears, but a fridge magnet is a permanent magnet that is always on. [5 marks]
Model answer: Leo winds insulated wire into a coil round an iron nail and joins the ends to a low-voltage cell, never mains, which is dangerous. The magnetism comes from the current, so disconnecting the cell makes it disappear. A fridge magnet is permanent: always on.
Common error: field lines drawn S to N, or crossing.