Electric & Magnetic Fields
Electric & Magnetic Fields is a free interactive simulation from StudyFi Lab. It runs right in your browser, with no sign-up and nothing to install.
Field lines, charges, currents and the Lorentz force
Experiments
Electric field of charges
Every charge creates a field of strength E = k·Q/r² that points away from a positive charge and towards a negative one. The fields of several charges add up as vectors (superposition). Field lines start on positive charges and end on negative ones; the dashed equipotentials cross them at right angles. A test charge q feels the force F = q·E.
Try this: Choose the like pair and move the test charge exactly halfway between them — the force drops to zero.
Magnetic field of wires
A straight wire carrying current I is perpendicular to the screen: ⊙ means the current flows out towards you, ⊗ means it flows in. Around it the magnetic field lines are concentric circles and the field strength is B = μ₀·I/(2π·r). The right-hand rule gives the direction: thumb along the current, fingers curl along the field. The fields of two wires add up as vectors, and the compass needles turn along the total field.
Try this: Turn on the second wire with the same current in the same direction and put the probe halfway between them — the field cancels there. Then reverse one current.
Lorentz force
A charged particle moving in a magnetic field feels the Lorentz force F = q·v·B at right angles to its velocity. The force only turns the motion and never changes the speed, so the particle goes round a circle of radius r = m·v/(|q|·B) with period T = 2π·m/(|q|·B). An added electric field E pushes the opposite way: at the speed v = E/B the two forces balance and the particle flies straight (a velocity selector).
Try this: Double the speed — the radius doubles, but the period T stays the same.
Frequently asked questions
What is Electric & Magnetic Fields?
Electric & Magnetic Fields is a free interactive simulation from StudyFi Lab. It runs right in your browser, with no sign-up and nothing to install. Field lines, charges, currents and the Lorentz force
Is Electric & Magnetic Fields free?
Yes. Electric & Magnetic Fields is completely free. It works in the browser on computers, tablets and phones, and you do not need an account.
What can I explore in Electric & Magnetic Fields?
Electric field of charges, Magnetic field of wires, Lorentz force.
What does the “Electric field of charges” experiment show?
Every charge creates a field of strength E = k·Q/r² that points away from a positive charge and towards a negative one. The fields of several charges add up as vectors (superposition). Field lines start on positive charges and end on negative ones; the dashed equipotentials cross them at right angles. A test charge q feels the force F = q·E.
What does the “Magnetic field of wires” experiment show?
A straight wire carrying current I is perpendicular to the screen: ⊙ means the current flows out towards you, ⊗ means it flows in. Around it the magnetic field lines are concentric circles and the field strength is B = μ₀·I/(2π·r). The right-hand rule gives the direction: thumb along the current, fingers curl along the field. The fields of two wires add up as vectors, and the compass needles turn along the total field.
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