Ohm's law you can watch. Wire a battery to three resistors, flip them between series and parallel, and see the current flow — faster where the current is bigger. Every value comes straight from V = I·R: the total resistance (add in series, reciprocals in parallel), 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. It all runs on your device.
Series = one loop, shared current. Parallel = separate branches, shared voltage.
Total resistance—
Total current—
Total power—
Arrangement—
One law runs the whole circuit: V = I·R. Put resistors in a single loop — series — and the same current threads through all of them while the battery's voltage splits up; the resistances simply add. Give each its own branch — parallel — and every resistor gets the full voltage while the current divides, so the total resistance drops below the smallest one and the battery pushes out more current. Same three resistors, two arrangements, completely different currents — and Ohm's law predicts every number.
How It Works
Ohm's law, two ways to wire resistors, and the power that follows.
1
Ohm's law
For any resistor, voltage, current and resistance are tied together by 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 is Ohm's law applied to one resistor or to the circuit as a whole.
2
Series vs parallel
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. Flip the toggle and watch both change.
3
Current and power
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. The flowing dashes run faster on wires carrying more current, so you can see where the current is largest.
What is Ohm's law?
Ohm's law states that the current through a resistor is proportional to the voltage across it: V = I·R (so I = V/R and R = V/I), with V in volts, I in amperes and R in ohms. It lets you find any one quantity from the other two, and this simulator applies it to every resistor as you change the battery and resistances.
How do series and parallel circuits differ?
In series, resistors share one loop: the same current flows through each and the voltage divides, with R_total = R₁ + R₂ + R₃. In parallel, each resistor is its own branch across the battery: each gets the full voltage and the current splits, with 1/R_total = 1/R₁ + 1/R₂ + 1/R₃. Toggle between them and watch the current and resistance change.
Why is total resistance smaller in parallel?
Adding a parallel resistor gives current another path, so more current flows for the same voltage — which means less total resistance. The conductances (1/R) add, so 1/R_total = 1/R₁ + 1/R₂ + 1/R₃, always below the smallest resistor: three 100 Ω in parallel give 33.3 Ω, versus 300 Ω in series.
How do you calculate power in a circuit?
The battery's power is P = V·I in watts, and for a single resistor also P = I²·R = V²/R. Because a parallel arrangement draws more current from the same battery, it dissipates more total power than the same resistors in series — the simulator shows the total power updating as you switch modes.