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.
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The magnetic field inside a long solenoid is uniform and parallel to the axis of the solenoid.
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.
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.
When a ferromagnetic material, such as iron, is placed inside a solenoid, it significantly increases the strength of the magnetic field generated.
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?
$\mu_0$ (permeability of free space) quantifies how much resistance is encountered when forming a magnetic field in vacuum. Ferromagnetic materials have higher permeability.