The rate at which a capacitor charges or discharges will depend on the resistance of the circuit. Resistance reduces the current which can flow through a circuit so the rate at which the charge flows will be reduced with a higher resistance. This means increasing the resistance will increase the time for the capacitor to charge or discharge.
A capacitor has an infinite resistance (well, unless the voltage gets so high it breaks down). The simplest capacitor is made from two parallel plates with nothing but space in between - as you can guess from its electronic symbol. In a DC circuit, a capacitor acts as an open circuit and does not permit current to pass.
Placing a resistor in the charging circuit slows the process down. The greater the values of resistance and capacitance, the longer it takes for the capacitor to charge. The diagram below shows how the current changes with time when a capacitor is charging.
After five time constants, the capacitor is almost fully charged, at 99%. The larger the time constant, the slower the capacitor charges, making it crucial for designing circuits that require specific charge rates. Capacitor Discharge Time Constant: The capacitor discharge time constant governs how quickly the capacitor loses its stored charge.
Capacitor Time Constant Formula: The formula for the Capacitor Time Constant is τ = R × C, where τ (tau) represents the time constant, R is the resistance in ohms, and C is the capacitance in farads. This simple yet powerful equation helps you calculate the time it takes for a capacitor to charge or discharge in an RC circuit.
Capacitor Charge Time Constant: The capacitor charge time constant refers to how quickly a capacitor charges through the resistor in a circuit. It takes about one capacitor time constant (τ) for the capacitor to reach 63% of its maximum voltage. After five time constants, the capacitor is almost fully charged, at 99%.