---
title: "Solenoid — AP Physics C: E&M Definition & Exam Guide"
description: "A solenoid is a tightly wound cylindrical coil that produces a uniform field B = μ₀nI inside. Learn how Ampère's law derives it and how FRQs test it."
canonical: "https://fiveable.me/ap-physics-c-e-m/key-terms/solenoid"
type: "key-term"
subject: "AP Physics C: E&M"
---

# Solenoid — AP Physics C: E&M Definition & Exam Guide

## Definition

A solenoid is a coil of wire wound tightly in the shape of a cylinder, often with an iron core inside, used to generate strong magnetic fields when electric current flows through it.

## Related Study Guides

- [4.4 Biot–Savart Law and Ampère’s Law](/ap-physics-c-e-m/unit-4/biot-savart-law-amperes-law/study-guide/HChNR7z7O4ql5SF8879S)
- [Exam Guide](/ap-physics-c-e-m/unit-upxYXpRI8Y0mOaI0/frqmcq-exam-guide/study-guide/ehvHVDDTHtSxAyWD2bWl)

## Review

### Related Terms

- [Electromagnetic Induction](/ap-physics-c-e-m/key-terms/electromagnetic-induction): The process of generating an electric current in a circuit by changing the magnetic field passing through it.
- [Ampere's Law](/ap-physics-c-e-m/key-terms/amperes-law): Relates the magnetic field around a closed loop to the electric current passing through that loop.
- Magnetic Flux Density: A measure of the strength of a magnetic field, often denoted as B.