- When a capacitor in series with a resistor discharges,
the charge on its plates decreases exponentially
q(t) = q0 * exp(-t/RC)

- The current created by the capacitor also decreases exponentially
from its initial value
I(t) = I0 * exp(-t/RC)

- The product of resistance and capacitance, RC, is called the
*time constant*of the circuit. The current and charge change by a factor of e (= 2.718) for every time constant which passes - Charging a capacitor goes quickly at first, then slows down
and approaches a limiting value
q(t) = q0 * [ 1 - exp(-t/RC) ] = CV * [ 1 - exp(-t/RC) ]

where**V**is the voltage of the battery charging the capacitor - The current flowing as a capacitor charges is large at first,
but decreases with time
I(t) = I0 * exp(-t/RC) = (V/R) * exp(-t/RC)

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Copyright © Michael Richmond. This work is licensed under a Creative Commons License.