(i) With a neat labelled diagram, describe the pattern of the magnetic field produced by a current-carrying solenoid. How does the field inside the solenoid differ from the field outside it?
(ii) What is an electromagnet? Name the material used for its core and give one reason why that material is preferred.
(iii) List any two applications of electromagnets in everyday life.
Generated by claude-sonnet-4-6 · 2026-06-26 01:11 · grounding rag
Model Answer
(i) Magnetic Field due to a Current-Carrying Solenoid:
A solenoid is a coil of many turns of insulated copper wire wound in the shape of a cylinder.
Diagram:
```
N |====|====|====|====| S
→ field lines inside (parallel, uniform)
field lines outside resemble a bar magnet
```
(Diagram shows parallel field lines inside and curved lines outside, with N and S poles marked.)
- Inside: Field lines are parallel and straight → field is uniform.
- Outside: Field pattern resembles that of a bar magnet; one end acts as N-pole, the other as S-pole.
(ii) Electromagnet:
An electromagnet is a magnet formed by placing a piece of soft iron inside a current-carrying solenoid.
Core material: Soft iron.
Reason: Soft iron loses its magnetism as soon as the current is switched off (temporary magnet), making it suitable for electromagnets.
(iii) Two Applications of Electromagnets:
- Electric bells
- Cranes used in scrap yards to lift heavy iron/steel objects.
Source: Chapter 12, Section 12.2.4
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Explanation
- The diagram must be labelled with N-pole, S-pole, current direction, and field lines (inside straight/parallel, outside curved). Examiners award 1 mark for a correct labelled diagram.
- Key contrast: uniform inside vs bar-magnet pattern outside — both parts must be stated.
- For the electromagnet, naming soft iron and giving the reason (loses magnetism easily / temporary) are both needed for full marks.
- Any two valid real-life uses (electric bell, telephone earpiece, MRI, scrap-lifting cranes) are acceptable.