Basic Circuit Bench

Three experiments

Ohm's law · LED: change the supply voltage and resistance and the LED brightness and current change. Make the resistor too small and a warning appears above 20 mA. You can check the LED resistor formula R = (Vs − Vf) / I directly.

Voltage divider: the voltage splits in the ratio of R1 to R2. This is the circuit used to read a battery voltage with an ADC. Larger resistors cut the current but raise the output resistance, and the lab warns you about that too.

RC charging: switch on and the capacitor charges along an exponential curve; switch off and it discharges. The graph shows 63% at 1τ and nearly 100% at 5τ. Time is scaled so that one second on screen is 1τ.

Things to try

1. In the LED experiment, double the resistance and check that the current halves exactly.
2. In the divider experiment, find R1 and R2 that let a 3.3 V ADC read 12 V.
3. In the RC experiment, find several R and C combinations that give the same τ.