Science (086) — CBSE Class 10 board question

(i) A solenoid is a coil consisting of many circular turns of insulated copper wire wound closely in the shape of a cylinder. When current flows through it, it behaves like a bar magnet and produces a strong, uniform magnetic field inside it.

(ii) The magnetic field lines of a solenoid:

```
N S
|←←←←←←←←←←←←←←←←←←←←←←←|
| ———————————————————————— |
| ———————————————————————— |
|←←←←←←←←←←←←←←←←←←←←←←←|
```

The field lines inside the solenoid are parallel and equally spaced (uniform field), and outside they resemble the field of a bar magnet — emerging from the north end and merging at the south end.

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• (i) Define solenoid clearly — "many turns of insulated wire wound in cylindrical shape" earns the mark. Mention it acts like a bar magnet for full credit.
• (ii) Key features examiners look for in the diagram: parallel, equally-spaced lines inside (uniform field) and curved closed lines outside similar to a bar magnet. Label N and S poles. Since drawing cannot be shown perfectly in text, in the actual exam draw neat closed curved lines outside and straight parallel lines inside the coil shape.