Ohm’s Law Visual Explorer

Use voltage, current, and resistance to see how Ohm’s Law ties them together in a circuit. Enter two values to calculate the third and see the live relationship between them.

Ohm’s Law

V = I × R

Voltage (V) is the push that moves current through a circuit. Current (I) is how many charges pass a point each second, measured in amps (A). Resistance (R) slows the current and is measured in ohms (Ω). Every time you double one value while holding a second steady, the third responds proportionally.

Try changing the sliders below; the script will compute the missing value and explain how the numbers relate.

Interactive Calculator

Enter any two values above.

Try this scenario

A flashlight battery supplies 3 volts to a bulb with 0.15 amps running through it. Plug those two values into the calculator and you’ll discover the bulb’s resistance. If you then increase the resistance to 40 Ω, notice how current drops (because V stays the same).

This is the heart of Ohm’s Law: voltage drives the current, but resistance controls how much current can flow for a given voltage.

Series & Parallel Resistance Calculator

Enter resistor values (comma separated) and see how their totals behave when wired in series versus parallel. This helps you plan circuits and verify how much resistance you get from combined parts.

Series total: —

Parallel total: —

Resistance Color Code Picker

Choose two significant-band colors, a multiplier, and tolerance to decode a resistor's rating instantly. The result field also reminds you how to read the bands, and below it we store tips plus common misconceptions.

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Tips & common misconceptions

Always read the bands from left to right, with the tolerance band furthest from the leading end.

Don't assume identical colors mean identical value—double-check the multiplier (gold/silver can look like other metallic finishes).

Resistance is rarely exact; use the tolerance band to understand the minimum/maximum range.