Hi guys I'm waaay out of my depth and could do with some

>>305222
>>305225
Don't you just plug the numbers in?

File: Exponential_Charge.jpg (35KB, 996x687px) Image search: [Google]

35KB, 996x687px

>>305225
(i) the plot of the voltage Vc against time is an "exponential charge" rising to approximately the full supply voltage ( 15V ) after a time ( t ) = 5CR seconds.

>math problem disguised as a physics problem
l m f a o

>>305222

(ii) a)
at t = 1.62ms, the instantaneous voltage across the capacitor will be given by:
Vc = 15 ( 1 - EXP( - 0.00162 / 0.001 ))
= 12.03 V

(ii) b)
at t = 3.86ms, the instantaneous voltage across the capacitor will be given by:
Vc = 15 ( 1 - EXP( - 0.00386 / 0.001 ))
= 14.68 V

>>305222

If the capacitance is doubled, the "time constant" (RC) will be doubled to 2ms and the larger capacitance will take twice as long to charge to any given voltage. The rate of change of capacitor voltage would drop to half the original values:

i.e. it would now take approximately 10ms for the larger capacitor to become virtually "fully charged" to the supply voltage (15V).

NB five times the time constant (5RC) is usually taken to be the practical point in time at which this type of exponential change reaches the final value.