Electricity and magnetism

Transformers and generators

Study generator and transformer in one model: vary the magnetic field and rotation rate to measure induced EMF. Verify $e=-N\,d\Phi/dt$ and the transformer ratio $U_2/U_1=N_2/N_1$ .

High school

⚠ Real devices involve dangerous high voltages — only observe models or isolated low-voltage demonstration kits.

Equipment

3D model of a coil rotating in a field / primary-secondary windings (two panels)
Magnetic-field/level and Angle/Speed sliders
EMF readouts and a Pause button per panel

Procedure

Observe the alternating EMF
In panel 1, run the rotating coil: the e(t) readout alternates sign each cycle because flux $\Phi=NBS\cos\omega t$ oscillates. Use «Pause» at the wave's peak and trough; e = 0 when Φ is maximal and e peaks when Φ = 0 — EMF tracks the flux derivative, not the flux.
Verify dependence on B and rate
At fixed speed, raise «Magnetic field» and record the amplitude e_max: proportional to B. At fixed B, vary «Angle/Speed»: e_max scales with ω via $e_{max}=NBS\omega$ . Two sweeps give two datasets — a quantitative check of Faraday's law.
Transformer ratio
In panel 2, watch the secondary winding pick up the primary's shared flux. Change the «level» (turns/intensity) and read both voltages: check $U_2/U_1=N_2/N_1$ — step-up for N₂ > N₁, step-down for N₂ < N₁; ideal power is conserved $U_1I_1=U_2I_2$ .
Connect to power transmission
Explain why grids step voltage up for long transmission: loss $P_{loss}=RI^2$ falls with the square of current, so raising U (lowering I at fixed power) saves enormously. Predict U₂ and I₂ for a chosen turns ratio, then verify on the model.

Simulation

Experiment history

Michael Faraday discovered electromagnetic induction in 1831 at the Royal Institution: a magnet moving through a coil produced a transient current — and his «Faraday disc», the first DC generator, spun a copper disc between magnet poles. He also built a primitive transformer: two windings on an iron ring, proving a shared flux transfers EMF. Industrialization came in the later 19th century: Pixii (1832) and Gramme (1871) built usable generators; Gaulard and Gibbs (1882), then Zipernowsky–Déri–Bláthy (1885), perfected AC transformers — the foundation of the «war of currents» that the Westinghouse–Tesla AC system won through efficient high-voltage transmission, still the backbone of today's grid.

Related physicists

Michael Faraday James Clerk Maxwell

Equipment

Procedure

Simulation

Experiment history

Related physicists

Related library topics