physics / Electricity & Magnetism / free

Magnetic Fields

Change current and motion to see field and force respond.

Follow the mechanism1 / 3

Charge is moving through a field. A magnetic field acts on moving charge, not on a stationary charge in this model.

current creates a magnetic fieldB ∝ I / r · F = q v × B

Focus the idea

field strength2.50

distance2 m

charge force25.00

directionup

Current 5 ADistance 2 mMoving charge 2Charge speed 5 m/s

Doubling distance weakens this field model by the same inverse factor; current sets the field’s strength.

Positive current flows up the wire and the charge moves to the right, away from the wire. ⊗ marks field into the page and ⊙ out of it; the field lines are closed circles around the wire. A stationary charge feels no magnetic force.

04 / PRACTICE

Make the idea yours.

0 / 3 checked

Use the model, then answer without looking back. Each check isolates one decision a learner should be able to make after this lesson.

CHECK 1 / 3

Magnetic Fields

Make the idea yours.

What magnetic force acts on a stationary charge?