The field of a current loop and a solenoid in 3D

Direct answer

See 3D magnetic field lines of a circular loop and a solenoid from the Biot–Savart law, and read B anywhere on the axis.

Field lines are closed loops computed from the Biot–Savart law. Inside a solenoid they are nearly straight and evenly spaced, so the field is uniform.

Simulation

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Magnetic Field of a Current Loop and Solenoid (3D)

Magnetic effects

Source Loop

Current I (A) 5 A

Radius R (cm) 2.5 cm

Turns N 50

Probe on axis x (cm) 0 cm

Drag to rotate, two fingers or right-drag to pan, scroll or pinch to zoom. The toolbar has views, cutaway, measure and “show the maths”.

What's happening? Field lines are closed loops computed from the Biot–Savart law. Inside a solenoid they are nearly straight and evenly spaced, so the field is uniform.

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Where it is in NCERT: Class 12 Physics Part I, “Moving Charges and Magnetism” (Magnetic force on a current-carrying conductor, Motion in a magnetic field, Ampere's circuital law, The solenoid and the toroid); Class 12 Physics Part I, “Magnetism and Matter” (The bar magnet, Magnetism and Gauss's law, Magnetisation and magnetic intensity, Magnetic properties of materials) · ncert.nic.in
Topic notes and formulas: Magnetic Effects of Current and Magnetism
Printable formula sheet
Chapter-wise JEE Main PYQs (14)