In a series circuit with 9V and three equal 100Ω resistors, what is the voltage across each?

Total R = 300Ω, I = 9/300 = 30mA, V = IR = 3V each.

Three 300Ω resistors in parallel across 9V — what is the total current?

R_eq = 100Ω, I_total = 9/100 = 90mA.

Apply KCL at the top node of a parallel circuit to find the branch currents.

I_total = I₁ + I₂ + I₃; each branch: I = V/R.

Pro 🔒~30 min

DC Circuit Virtual Lab

Build and measure DC circuits with a virtual breadboard

How it works

Kirchhoff's laws govern DC circuit analysis. KVL states that the sum of voltage drops around any closed loop equals zero (energy conservation). KCL states that the sum of currents at any node equals zero (charge conservation). Together they allow systematic solution of any DC circuit. Ohm's Law (V=IR) connects voltage, current, and resistance at each element.

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Step-by-step

Drag components onto the virtual breadboard and connect them with wires.
Use the multimeter to probe voltages and currents.
Switch between series and parallel configurations.
Verify KVL by summing voltages around a loop.

Key formulas

$V = IR$ Ohm's Law
$\sum V = 0$ Kirchhoff's Voltage Law (KVL)
$\sum I = 0$ Kirchhoff's Current Law (KCL)

Frequently asked questions

In a series circuit with 9V and three equal 100Ω resistors, what is the voltage across each?: Total R = 300Ω, I = 9/300 = 30mA, V = IR = 3V each.
Three 300Ω resistors in parallel across 9V — what is the total current?: R_eq = 100Ω, I_total = 9/100 = 90mA.
Apply KCL at the top node of a parallel circuit to find the branch currents.: I_total = I₁ + I₂ + I₃; each branch: I = V/R.