What is Coil and solenoid? — Physics

Definition 15.9 High School Physics · Chapter 15 — Magnetism and Magnetic Fields

Winding the wire concentrates its field. A flat coil ( $N$ turns in a disc) behaves like a thin magnet, one face north, the other south; a solenoid — a long cylindrical winding, $n$ turns per metre — like a bar magnet.

A solenoid cut lengthwise (/: the turns crossing the page): inside, a uniform B = _0 n I along the axis; outside, a weak, spread-out return field (dashed). — A solenoid cut lengthwise ( $\odot$ / $\otimes$ : the turns crossing the page): inside, a uniform $B = \mu_0 n I$ along the axis; outside, a weak, spread-out return field (dashed).

Examples

Example 15.13 (Solenoid numbers)

At $10$ turns per centimetre ( $n = 1000\,\mathrm{m}^{-1}$ ) and $I = 5.0\,\mathrm{A}$ : $B = 1.26 \times 10^{-6} \times 1000 \times 5.0 \approx 6.3\,\mathrm{mT}$ — a hundred Earth fields, adjustable by a knob.

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Examples

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