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Capacitors and RC

Hi guys,

I'm stuck on a question assigned by my teacher. We've been given t1/2 (15s), V0 (6V) V (3V) and told to calculate RC, then give values for R and C that would give a time constant of 10 seconds. this even possible? Surely there are too many unknowns?

Posted from TSR Mobile
Original post by xloichan
Hi guys,

I'm stuck on a question assigned by my teacher. We've been given t1/2 (15s), V0 (6V) V (3V) and told to calculate RC, then give values for R and C that would give a time constant of 10 seconds. this even possible? Surely there are too many unknowns?

Posted from TSR Mobile
Resistors and capacitors are manufactured in a range of 'preferred' (standard) values.

For instance, the so called 'E24' preferred range of resistors (+/-5% tolerance limit) has 24 standard values for every decade of resistance (x10 factor). Other common ranges are E12(10%), E48(2%), E96(1%) and E192(0.5%).

Capacitors have similar ranges of values.

Have a look at this chart for the E24 resistor range: http://ecee.colorado.edu/~mcclurel/resistorsandcaps.pdf

The time constant is the product of the capacitance and resistance.

t = CR

You can therefore choose any two component values from the 'preferred' list so that the required CR is achieved. :smile:
(edited 9 years ago)

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