Generated by claude-sonnet-4-6 · 2026-06-15 06:47 · grounding rag
Model Answer
(i) Diagram of Magnetic Field Lines in a Solenoid:
```
N S
|→→→→→→→→→→→→→→→→→→→→→→→→→→→|
| |
←←←←←←←←←←←←←←←←←←←←←←←←←←
```
(Field lines are parallel and straight inside, and loop around outside like a bar magnet.)
Two salient features:
- Inside the solenoid, field lines are parallel and equidistant, indicating a uniform magnetic field.
- The field pattern outside is similar to a bar magnet; one end behaves as North pole and the other as South pole.
(ii) Electromagnet:
An electromagnet is a temporary magnet that works only when electric current flows through it.
How it is made: A long insulated copper wire is wound in the form of a coil (solenoid) around a soft iron core. When current passes through the coil, the soft iron core gets strongly magnetised and acts as a magnet. When the current is switched off, it loses its magnetism. Electromagnets are used in electric bells, cranes, and MRI machines.
Source: Chapter 12 – Magnetic Effects of Electric Current, Sections 12.1 and 12.2
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Explanation
- For the diagram, draw a solenoid with several turns; show straight parallel lines inside and curved closing lines outside (like a bar magnet). Label N and S poles. Even a rough but labelled diagram earns full marks.
- Examiners look for two distinct features — uniform field inside and bar-magnet-like field outside are the standard expected points.
- For the electromagnet, the two key ideas are: (a) definition (temporary magnet using current) and (b) construction (insulated coil wound over soft iron core). Soft iron is used because it loses magnetism when current stops — this is often asked as a follow-up.
- Keep the answer concise; this part is worth ~2 marks so 3–4 lines suffice.