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Physics · 术语表

什么是 Coil and solenoid?

又称: coil · solenoid

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

Winding the wire concentrates its field. A flat coil (NN turns in a disc) behaves like a thin magnet, one face north, the other south; a solenoid — a long cylindrical winding, nn 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=μ0nIB = \mu_0 n I along the axis; outside, a weak, spread-out return field (dashed).

示例

Example 15.13 (Solenoid numbers)

At 1010 turns per centimetre (n=1000 m−1n = 1000\,\mathrm{m}^{-1}) and I=5.0 AI = 5.0\,\mathrm{A}: B=1.26×10−6×1000×5.0≈6.3 mTB = 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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