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Capacitor in Direct Current Circuit

These online calculators computes various parameters for charging and discharging the capacitor with the resistor

These online calculators computes various parameters for charging and discharging the capacitor with the resistor. Formulae used for calculations are below the calculators.

Created on PLANETCALC

Charging the Capacitor with a Resistor

Digits after the decimal point: 2
Time Constant, milliseconds
 
5 Time Constants (99.2% charged), milliseconds
 
Initial Current, Amperes
 
Maximum Power Dissipation, Watts
 
Capacitor Voltage, Volts
 
Capacitor Charge, microCoulombs
 
Capacitor Energy, milliJoules
 
Power Supply Work, milliJoules
 



Created on PLANETCALC

Discharging the Capacitor with the Resistor

Digits after the decimal point: 2
Initial Capacitor Energy, milliJoules
 
Initial Capacitor Charge, microCoulombs
 
Time Constant, milliseconds
 
Initial Current, Amperes
 
Maximum Power Dissipation, Watts
 
Final Capacitor Charge, microCoulombs
 
Final Capacitor Energy, milliJoules
 
Final Capacitor Voltage, Volts
 



Below is the picture of electrical circuit for charging the capacitor with the power supply unit.

capacitor.jpg



After switch K is closed, direct current starts charging the capacitor.
According to Ohms law, the sum of capacitor and resistor voltages is equal to power supply voltage.

\epsilon=IR+\frac{q}{C}

The capacitor charge and current depend on time. At the initial moment, there is no charge at the capacitor, thus, current is maximum, as well as power dissipation on the resistor.

I=\frac{\epsilon}{R}, P=I^2R

During charging, capacitor voltage changing according to the following equation

V(t)=\epsilon(1-e^{-\frac{t}{RC}})

where tau

\tau=RC

is called Time Constant. Since charging is infinite process, usually, a capacitor is considered to be fully charged after 5 time constants. After 5 time constants, the capacitor will be charged to 99.2% of the supply voltage.
Capacitor Charge

Q=CV

Capacitor Energy

W=\frac{Q^2}{2C}

Work of Power Supply

A=Q\epsilon

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