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Which of the following statements regarding the magnetic field produced by a current-carrying solenoid is INCORRECT?
The magnetic field inside the solenoid is uniform.
The magnetic field lines inside the solenoid are parallel straight lines.
The strength of the magnetic field depends on the number of turns in the coil.
The magnetic field is strongest at the center of the solenoid and zero at the ends.
The magnetic field is strongest at the center of the solenoid and zero at the ends.
A solenoid is a long coil of insulated wire wound in the form of a helix. The magnetic field inside a long solenoid is uniform and strong, while at the ends, it reduces to exactly half the value of the field at the center.
A solenoid is a long coil of insulated wire wound in the form of a helix. The magnetic field inside a long solenoid is uniform and strong, while at the ends, it reduces to exactly half the value of the field at the center.
Think of a solenoid like a tunnel; the wind (magnetic field) is constant and strong throughout the length of the tunnel, but as you exit the tunnel, the wind velocity drops significantly as it spreads into the open air.
B=μ0nI — Magnetic field inside a long solenoid
Bends=21μ0nI — Magnetic field at the ends of the solenoid
When current flows through the coil, each turn acts as a small current loop. The magnetic fields of these individual loops add up, creating a uniform field inside directed along the axis. At the ends, the field lines spread out into space, causing the intensity to decrease significantly, but it is not zero.
The magnetic field inside a long solenoid is uniform in both magnitude and direction.
Magnetic field lines inside a solenoid are parallel to the axis of the solenoid.
The strength of the field B is directly proportional to the number of turns per unit length (n) and the current (I).
The magnetic field is not zero at the ends; it is approximately half of the intensity at the center.
Provides a controlled, uniform magnetic field for experiments.
Easily adjustable magnetic field strength by changing current.
Magnetic field drops significantly outside the coil area.
Requires high current for strong magnetic fields.
Electromagnets for lifting heavy metallic objects.
Magnetic resonance imaging (MRI) machines.
μ0 is the permeability of free space, approximately 4π×10−7 T m/A.
Option D is incorrect because the field at the ends is 21Bcenter, not zero.
D is correct — The magnetic field inside a solenoid is strongest at the center and is NOT zero at the ends; it is approximately half the central value.
Remember that for any long current-carrying coil, the magnetic field is always strongest inside the core and tapers off as you move towards the open ends.