How long will a capacitor connected directly to supply without resistor charge?

[abdulhafeez]

in how much time the capacitor will charge while it is connected directly to the supply without any resistor ! only a capacitor with the supply

 

[nan_ishan]

Re: charging time

It will charge at atime of (Internal resistance of source)*(Value of capacitor) sec.

For ex.

1µF will charge in (Internal resistance of source)µsec.

Hope u got it

 

[A.Anand Srinivasan]

Re: charging time

it depends on the output resistance of the supply... it is like that resistor being in series with the capacitor...

 

[e_eja]

Re: charging time

it's depend on your resistance source and un ideal resistance on capacitor it's self

 

[saas123qa]

Re: charging time

you can assume it will charge at once because hte internal resistance is small

 

[Pavel_S]

Re: charging time

Exactly, voltage on charged capacitor is given by formula (assuming that, before charging capacitor was fully discharged):

Uc=Ucc*(1-exp(-t/RC))

Uc - capacitor voltage
Ucc - source voltage
C - capacitance in Farads
R - resistance in ohms

Resistance ever exist - it is sum of internal source resistance, wires resistance, connectors resistance, capacitor leads resistance, internal capacitor resistance, additional series resistance.

Values of above mentioned resistancem may be different from part of miliohms (wires, capacitor leads) to megaohms (additional resistors).

T=R*C - time constant

t=K*T

K=0 -> Uc=0
K=1 -> Uc=0.632*Ucc
K=2 -> Uc=0.864*Ucc
K=3 _> Uc=0.95*Ucc
....

t=2.3*T -> Uc=0.9*Ucc
t=4.6*T -> Uc=0.99*Ucc
t=6.9*T -> Uc=0.999*Ucc

For example: R=1Ω, C=100µF

t for Uc=0.999*Ucc is equal 6.9*1Ω*100µF=0.69 ms

 

[nguyennam]

Re: charging time

Instantly, as our guys showed.

It is quite dangerous to connect the capacitor directly to the power supply without a current limiting resistor, especially when large capacitance and high voltage.