Solve electric circuits using Ohm’s law, Kirchhoff’s laws, series and parallel resistors.
An electric circuit calculator computes voltage, current, resistance, and power in DC circuits using Ohm's law and Kirchhoff's laws. Handles series and parallel resistor combinations, voltage dividers, and power calculations — the fundamentals needed for every circuit design from LED indicator to a power amplifier.
Modern circuit analysis software (SPICE) handles complex nonlinear circuits, but for linear DC and simple AC analysis, the equations are easy to apply by hand and a calculator just speeds up the arithmetic.
V = IR \;;\; P = VI = I^2 R = V^2/R
Inputs: 12 V supply driving 3 LEDs (each Vf = 2 V, If = 20 mA) in series with a current-limiting resistor
Compute the power dissipated using P = V² / R or P = I² × R. Choose a resistor rated at least 2× that power for safety margin. Common ratings: 1/8 W, 1/4 W, 1/2 W, 1 W, 5 W. For a 100 Ω resistor with 12 V across it, P = 144/100 = 1.44 W — use a 5 W resistor (1 W would overheat and burn out).
mAh measures capacity at a given voltage. Energy in joules = V × Q (charge in coulombs) = V × (mAh × 3.6). A 3,000 mAh phone battery at 3.7 V holds 3,000 × 3.7 × 3.6 = 39,960 J ≈ 11 Wh. The industry uses mAh because phone designers care most about runtime at the device's standard voltage, not absolute energy.
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