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What is the term for a long coil consisting of a large number of turns of insulated copper wire wound on a soft iron core, used to produce a uniform magnetic field?
Electromagnet
Solenoid
Toroid
Inductor
Solenoid
A solenoid is a long coil of many circular turns of insulated copper wire wound in a cylindrical shape. When an electric current flows through it, it produces a uniform magnetic field along its axis, similar to that of a bar magnet.
A solenoid is a long coil of many circular turns of insulated copper wire wound in a cylindrical shape. When an electric current flows through it, it produces a uniform magnetic field along its axis, similar to that of a bar magnet.
Think of a solenoid like a garden hose coiled up; just as the hose directs water in a specific path, the solenoid coils 'direct' the magnetic lines of force to form a concentrated, uniform field inside.
B=╬╝0тАЛnI тАФ Magnetic field inside an ideal solenoid, where ╬╝0тАЛ is the permeability of free space, n is the number of turns per unit length, and I is the current.
When current passes through the solenoid, each turn of wire creates its own magnetic field. Because the turns are closely wound, these individual fields add up, creating a strong and uniform magnetic field inside the coil. If a soft iron core is placed inside, it becomes magnetized by induction, significantly increasing the total magnetic flux density.
The magnetic field inside a long solenoid is uniform and parallel to the axis.
The strength of the field is directly proportional to the current and the number of turns per unit length.
A soft iron core inside a solenoid turns the device into an electromagnet.
The ends of the solenoid act like the North and South poles of a bar magnet.
Can produce a very strong and uniform magnetic field.
Magnetic field strength can be controlled by varying the current.
Requires continuous electrical power to maintain the magnetic field.
Produces heat due to resistance in the copper wire.
Electric bells and relays
Magnetic resonance imaging (MRI) machines
Electromagnetic door locks
| Feature | Electromagnet | Solenoid |
|---|---|---|
Core Material | Soft iron (to increase flux) | Air or non-magnetic material |
The constant ╬╝0тАЛ (permeability of free space) is approximately 4╧А├Ч10тИТ7┬аTтЛЕm/A.
Option A is an electromagnet, which is a solenoid with a magnetic core. Option C is a toroid, which is a solenoid bent into a circular ring shape. Option D is an inductor, a broad category of components that oppose changes in current.
B is correct тАФ A solenoid is defined as a long cylindrical coil of insulated wire used to generate a uniform magnetic field.
In competitive exams, remember that for a solenoid, the magnetic field is strongest inside and effectively zero outside (for an ideal infinite solenoid).