A series and parallel resistor calculator you can watch. Wire a battery to three resistors and flip them between series, parallel and a mixed network (R₁ in series with R₂‖R₃), and see the current flow — faster where the current is bigger. Every value comes straight from V = I·R: the equivalent resistance (add in series, reciprocals in parallel), worked out step by step, plus the current I = V/R, the voltage across each resistor and the power P = V·I. Change the battery or any resistor and the whole circuit re-solves live — copy the results in a click. It all runs on your device.
You are in the Physics lab.
Current & power vs battery voltage. With the resistors fixed, sweeping the battery voltage traces Ohm's law: the current I = V/R climbs in a straight line (blue), while the power P = V²/R curves upward as a parabola (amber). The dots mark where the present battery voltage sits on each curve — drag the battery slider and watch the operating point travel.
Per-resistor bar chart. In series the bars show the voltage drop across each resistor — a bigger resistor takes a bigger share, and the three add up to the battery voltage (Kirchhoff's voltage law). Switch to parallel and the bars become the current through each branch — a smaller resistor draws more, and the three add up to the total current (Kirchhoff's current law).
What the flowing dashes, the two arrangements and the readouts are each telling you.
The dashes crawling along the wires are the current, and their speed is proportional to how much current that wire carries — drop a resistance and watch them speed up. In a series loop every wire carries the same current, so the dashes move together; in parallel each branch runs at its own pace, fastest through the smallest resistor because it draws the most current.
Flip between the two and watch what stays fixed. In series the current is identical everywhere while the battery voltage divides among the resistors — that is the bar chart of voltage drops. In parallel the full battery voltage sits across every branch while the current splits — the same bar chart now reads branch currents. The battery on the canvas is always labelled with its voltage, each resistor with its value and its own drop or current.
Every number is consistent. The total current is I = V / R_total, the power is P = V·I, and each per-resistor readout is that resistor's own V = I·R. Add up the series voltage drops and you get the battery voltage; add up the parallel branch currents and you get the total current — Kirchhoff's two laws, live. Try Series 3×100 Ω (R_total 300 Ω, I 0.040 A) then Parallel 3×100 Ω (R_total 33.3 Ω, I 0.36 A) to see it.
Ohm's law, two ways to wire resistors, and the power that follows.
For any resistor, voltage, current and resistance obey V = I·R. Know two and you have the third: the current is I = V/R, and a bigger resistance means less current for the same voltage. Every reading in this simulator — the totals and each per-resistor drop or branch current — is Ohm's law applied to one resistor or to the whole circuit.
In series the resistors share one loop: the current is the same in each and the voltage divides, with R_total = R₁ + R₂ + R₃. In parallel each sits on its own branch across the battery: the voltage is the same on each and the current splits, with 1/R_total = 1/R₁ + 1/R₂ + 1/R₃, always less than the smallest resistor. Three 100 Ω resistors give 300 Ω in series but only 33.3 Ω in parallel.
The total current the battery pushes out is I = V/R_total, so the low resistance of a parallel network draws a large current — which is why parallel dissipates more power, P = V·I, than the same resistors in series. Use the presets to jump between the arrangements, or the voltage divider preset to see unequal resistors take unequal shares of the voltage.
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Record total resistance, total current, and the voltage or current across each resistor.
Series resistances add and share one current while splitting voltage; parallel resistances combine reciprocally (total below the smallest) and share one voltage while splitting current. Ohm’s law V = IR ties them together.
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