Solenoid

Definition

A solenoid is a coil of wire that generates a magnetic field when an electric current passes through it. It is commonly used to create controlled magnetic fields in devices like electromagnets and inductors.

5 Must Know Facts For Your Next Test

1. The magnetic field inside a long solenoid is uniform and parallel to the axis of the solenoid.
2. The strength of the magnetic field inside a solenoid is given by $B = \mu_0 n I$, where $n$ is the number of turns per unit length, $I$ is the current, and $\mu_0$ is the permeability of free space.
3. The direction of the magnetic field inside a solenoid follows the right-hand rule: if you curl your fingers in the direction of the current, your thumb points in the direction of the magnetic field.
4. When a ferromagnetic material, such as iron, is placed inside a solenoid, it significantly increases the strength of the magnetic field generated.
5. Solenoids can be used in various applications such as relays, valves, and electromagnetic switches.

Review Questions

• What formula represents the strength of the magnetic field inside a solenoid?
• How does inserting a ferromagnetic core affect the magnetic field inside a solenoid?
• Which rule helps determine the direction of the magnetic field in a solenoid?

Related terms

Electromagnet: A type of magnet whose magnetic field is produced by an electric current. Typically consists of wire wound into a coil around a ferromagnetic core.

Ampere's Law: $\int \mathbf{B} \cdot d\mathbf{l} = \mu_0 I_{enclosed}$; relates integrated magnetic field around a closed loop to current passing through that loop.

Permeability: $\mu_0$ (permeability of free space) quantifies how much resistance is encountered when forming a magnetic field in vacuum. Ferromagnetic materials have higher permeability.