When a 470 micro farad capacitor is discharged through a fixed resistor R, the pd across it decreases by 80% in 45 s. Calculate the time constant of the circuit
Using the equation V=V0e-t/RC where RC is the time constant to be calculated: We know that the pd decreases by 80%, therefore the pd remaining, V is 0.2*V0. Putting this into the equation above: 0.2=e-t/RC, rearranging for RC gives RC=-t/ln(0.2), and substituing t=45s, we have: RC=28 s. The answer reflects the time it takes for the potential difference across the resistor to decrease to 37% of its original value when the capacitor is discharged through it.
PK
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