Magnetism Lab

Everywhere

• Topic tabs (under the title) switch between simulations in this lab. Some topics have smaller buttons under the stage for their screens.
• Teach shows live equations with the current numbers and "What to notice" points. Practice gives a numeric problem and a quiz.
• Move the sliders or tap the chips in the right-hand panel. The readings box updates live.
• Pause / Restart control the animation. Clean view hides everything except the stage, for projecting or recording; press Esc to leave it.
• In Practice, type a number (e.g. 12.5 or 3.2e-10), press Check or Enter. Show it on the stage sets the simulation to that problem.
• Nothing is saved: scores reset when the page is reloaded.

Oersted & moving charge

• Compass round a wire: switch the current on, reverse it, and watch the ring of compasses turn. Add the Earth's field to see the needle settle between the two fields.
• Moving charge: a charge fired into a field bends in a circle of radius r = mv/qB. With B into the page a positive charge turns anticlockwise and an electron clockwise; flip the charge or the field and the turn reverses.

Biot–Savart law

• Current element: drag the point P anywhere. dB = (μ₀/4π)·I dl sinθ/r² is worked out with your numbers.
• Straight wire: B = μ₀I/2πa, with the 1/a graph beside it.
• Circular coil: B at the centre and on the axis; drag the point along the axis.

Ampère's law

• Wire: the Amperian loop with ∮B·dl = μ₀I. Solenoid: B = μ₀nI — change the turns and the length. Toroid: B = μ₀NI/2πr, and it is zero outside.

Force & torque

• Wire in a field: F = BIL sin θ, with the left-hand / F = IL × B directions drawn.
• Two parallel wires: same direction attract, opposite repel; F/L = μ₀I₁I₂/2πd, and the definition of the ampere.
• Current loop: τ = NBIA sin θ — the idea behind the moving-coil meter and the motor. Also the orbital electron and electron spin moments.

Hall effect

• Set B, I, thickness and carrier density; V_H = BI/nqt. Switch the carriers between electrons and holes to flip the sign of the Hall voltage.

Earth's magnetism

• Globe: drag the latitude; the dip angle follows tan δ = 2 tan(latitude).
• Elements: declination, dip and the horizontal component H = B cos δ, drawn as a 3-D box.

Magnetic materials

• Kinds: diamagnetic, paramagnetic and ferromagnetic samples in a field, with their susceptibility χ.
• Domains: raise H and watch the domains line up, giving the M–H curve and saturation.
• Hysteresis: the B–H loop for soft iron and steel; retentivity, coercivity and the loop area (energy lost per cycle).

Magnets

• Bar magnet: pole strength m, magnetic moment M = m·2l, and the field on the axis (2M/d³) against the field on the equator (M/d³).
• Electromagnet: switch it on and off, change the core between air, soft iron and steel, and see why soft iron is used for electromagnets and steel for permanent magnets.

Language

• Choose English or বাংলা once on the home page (top right); every lab then opens in that language — tabs, controls, readings, equations, notes, problems and quizzes.

Full guide with teaching tips: User manual (also as a PDF).