The magnetic field of a straight wire in 3D

Direct answer

See the circular magnetic field lines around a current-carrying wire in 3D and measure B at any distance.

Field lines are circles around the wire. Reverse the current and every arrow flips. The field at the yellow probe falls as 1/r.

Simulation

Magnetic effects

Current (A) 10 A

Distance (cm) 4 cm

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What's happening? Field lines are circles around the wire. Reverse the current and every arrow flips. The field at the yellow probe falls as 1/r.

Learn more

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)