Electricity 1 — DC Circuits

Capacitors — charging up

continues from lesson 4 — values defined earlier in the course stay live here

ELI5: a capacitor is a tiny bucket for charge. Through a resistor it fills exponentially — fast at first, then ever slower. The time constant τ = R·C sets the pace: after one τ it's 63% full, after five τ it's full for all practical purposes.

C_{1} := 100e-6 F

= 0.0001 F capacitance (100 µF)

\tau = R_{1} \cdot C_{1}

= 0.006 ohm F time constant

\tau_{n} = 0.006

the same τ as a plain number (s), for the plot

12 * (1 - exp(-x / tau_n))

capacitor voltage while charging toward 12 V (x in seconds)

Real-world hook: RC charging sets the blink rate of a flasher, debounces a button, smooths the ripple in a power supply, and times the windshield-wiper delay. Where next: Electricity 2 lets the voltage alternate.