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The RC time constant · τ = R × C

A capacitor charging through a resistor rises on a curve, not a step. The time it takes is set by the resistor and the capacitor together: one time constant, τ equals R times C, is how long it takes to reach 63% of the supply.

Vin (full) 63% time → (set by τ = RC)
One time constant
τ = 10 kΩ × 10 µF
100 ms
63% after 1τ = 100 ms
effectively full after 5τ = 500 ms

Raise the resistance or the capacitance and the curve stretches: the same 63% point arrives later. Lower them and it arrives sooner. The output flips on when the capacitor crosses its threshold, so R and C set the delay. This is the timing element inside a 555 timer, and it's behind many reset and debounce delays on a circuit board.