Find the missing DC quantity

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<section class="electrical"><div class="result"><span class="eyebrow" id="unknownLabel">Calculated power</span><div id="answer" class="big">24 W</div><p id="equation">P = 12 V × 2 A = 24 W</p><span class="chip">Steady DC · Nonnegative scalar magnitudes</span></div><form class="panel" id="form" novalidate><label for="mode">Find the unknown</label><select id="mode"><option value="">Choose the unknown</option><option value="W" selected>Power (W)</option><option value="A">Current (A)</option><option value="V">Voltage (V)</option></select><div class="row"><div><label id="firstLabel" for="first">Voltage (V)</label><input id="first" value="12" inputmode="decimal"><p id="firstError" class="error"></p></div><div><label id="secondLabel" for="second">Current (A)</label><input id="second" value="2" inputmode="decimal"><p id="secondError" class="error"></p></div></div><div class="buttons"><button class="primary" type="submit">Calculate</button><button type="button" id="reset">Reset</button></div><p id="feedback" class="error" role="status"></p></form></section>
<section class="panel below"><h2>One relationship, three questions</h2><div class="equations"><div><strong>P = V × I</strong><p>12 V × 2 A = 24 W</p></div><div><strong>I = P ÷ V</strong><p>24 W ÷ 12 V = 2 A</p></div><div><strong>V = P ÷ I</strong><p>24 W ÷ 2 A = 12 V</p></div></div><h3>Substitution record</h3><pre class="record" id="record"></pre><p class="muted">Fictional educational values. Two known quantities are required; 10 W alone cannot determine volts. Inverse equations require a positive denominator. No AC, RMS, power factor, wiring, ratings, efficiency or energy/runtime inference.</p><p class="muted">Manual input scope: 0–1,000,000; at most six decimal places. Values use only the units shown. Tiny positive results retain scientific notation; approximate displays have up to six decimal places.</p><a href="https://openstax.org/books/physics/pages/19-4-electric-power">OpenStax: P = IV relationship</a></section><footer class="muted below">Local working copy · Changes are not saved after this page closes.</footer></main><script data-app>
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