= Electricity generation
<Electricity generation> converts another form of <energy> into electrical <energy> supplied to an <electrical load> or <electric power system>. A rotating <electrical generator> uses <electromagnetic induction>; a <solar cell> instead converts incident radiation through the <photovoltaic effect>. Neither process creates <energy>. The relevant input and output boundaries determine which losses enter a quoted conversion fraction.
For an original ideal rotating-coil model, let $N$ turns of area $A$ rotate at constant <angular velocity> $\omega$ in a uniform <magnetic field> $B$. With the coil normal initially aligned with that field, the linked <magnetic flux> and induced <electromotive force> are
$$
\Phi_{\rm linked}=NBA\cos(\omega t),\qquad
\mathcal E=-\frac{d\Phi_{\rm linked}}{dt}=NBA\omega\sin(\omega t).
$$
For $N=100$, $A=0.01\,\mathrm{m^2}$, $B=0.5\,\mathrm T$ and $\omega=100\,\mathrm{rad\,s^{-1}}$, the peak is $50\,\mathrm V$ and the sinusoidal <root mean square> value is $50/\sqrt2\approx35.36\,\mathrm V$. Doubling the speed doubles both the amplitude and <frequency> in this model. The DOE exposition develops the rotating-conductor waveform and distinguishes peak from effective values.<DOE Fundamentals Handbook Electrical Science>[Volume 3, Module 7, AC Generation Analysis, printed pp.1–6, sinusoidal generation and effective values]{ref}
An open-circuit induced <electric potential difference> does not specify deliverable <power>. On connecting a load, the resulting <electric current> produces an opposing electromagnetic <torque>; sustained electrical output requires corresponding mechanical input and provision for losses. For a stipulated steady shaft input of $2.0\,\mathrm{kW}$ and combined losses of $0.2\,\mathrm{kW}$, output is $1.8\,\mathrm{kW}$ and the shaft-to-electrical conversion fraction is $0.9$. This fraction excludes any earlier conversion from fuel or another primary supply into shaft <power>.
A proposed demonstration couples a small <electrical generator> to a controllable drive, measures rotational speed and open-circuit waveform, then applies several known <electrical loads> while recording shaft <torque>, <electric current> and terminal <electric potential difference>. The additional mechanical effort under load tests the <electromechanical conversion power balance>; an open-circuit waveform alone cannot test that balance.
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