Circuits you can open and run

A single resistor across a 9 V battery — the cleanest demonstration of V = I × R.

Why an LED needs a resistor — and how to size it for a target current.

Two equal resistors split 12 V into 6 V — the workhorse of analog design.

Three resistors in a line add up — same current everywhere, voltages that sum to the supply.

Two 1 kΩ resistors in parallel behave like a single 500 Ω — currents add, voltage is shared.

A capacitor charging through a resistor — the classic exponential, plotted on the scope.