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Magnetic field of moving charge
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Field from a charge in motion.
B = μ₀qv×r̂/4πr²A point charge with velocity v produces B = (μ₀/4π) q v × r̂/r² (for v ≪ c). The field forms circles around the line of motion.
An electron beam creates a field.
Only valid at low speeds.
In more detail
A moving charge produces a magnetic field, B = (μ0/4π) qv × r̂ / r², for low speeds. This field is part of the Biot-Savart law at the level of individual charges.
Real-world uses
- Electron beams in devices produce magnetic fields that can be measured.
- It explains the magnetism of currents in atoms.
- Physicists use the field of a moving charge to understand the origin of magnetism from relativity.
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Frequently asked questions
Is the field from a single charge measurable?
It is extremely small, so it is rarely measured directly.
Why is magnetism relativistic?
Magnetism arises from the relative motion of charges, which relativity links to electric fields.
Is magnetism a separate force from electricity?
No. Magnetism is a relativistic effect of moving charges, so the electric and magnetic forces are two aspects of one interaction.
Related topics in Magnetism & Induction
Aurorae · Van Allen belts · Superconducting magnets · Hall effect and sensors · Magnetic energy density · Magnetic pressure