what percentage of current remains in the resistor?

[charmcaster.engg]

After a capacitor has charged for 1 tc, what percentage of current remains in the resistor?

 

[davenn]

what resistor ?

please show us the circuit

 

[Gryd3]

After a capacitor has charged for 1 tc, what percentage of current remains in the resistor?

Perhaps you are asking for the percentage of charge in the capacitor instead of a percentage of current in a resistor?

 

[davenn]

who knows ? ... as I said ... lets see a circuit

 

[Arouse1973]

Perhaps you are asking for the percentage of charge in the capacitor instead of a percentage of current in a resistor?

No I think he's right. It's just strange he uses the word remains.
Adam

 

[hevans1944]

The current in the resistor has dropped to about 37% of the initial charging current after one time-constant of time has elapsed.

The relevant equation is Ir = (Vsource / R) (e^(-t/RC)) where Vsource is the voltage applied to the RC circuit, R is the resistance in ohms, C is the capacitance in farads, and t is the time elapsed in seconds, e is the base of natural logarithms (about 2.7182818284590452353602874713527), and the caret ^ indicates exponentiation.

Thus, for one time-constant of elapsed time, RC = t and therefore t / RC = 1. The initial current, which is (Vsource / R), is therefore reduced by the factor (e^(-1)) which is about 0.36787944117144232159552377016146 or (roughly) 37%. For more basic information on RC charging (and discharging) see this link.

Since this is homework, I really shouldn't be telling you any of this. Google is your friend.