A circuit that contains only capacitance is commonly referred to as an RC circuit, which stands for Resistor-Capacitor circuit. In this type of circuit, a resistor (R) and a capacitor (C) are connected together in various configurations to create different types of electrical behaviors.
Capacitance is the ability of a component (capacitor) to store an electric charge. When a voltage is applied across a capacitor, it charges up by accumulating electrons on one of its plates and creating an equal and opposite charge on the other plate. The voltage across the capacitor increases gradually as it charges up, and it decreases when the capacitor discharges.
Here are a few configurations of RC circuits:
RC Charging Circuit:
In this circuit, a resistor and a capacitor are connected in series. When a voltage is suddenly applied across the circuit, the capacitor starts charging up. The voltage across the capacitor increases exponentially, and the rate of charging gradually slows down as the capacitor approaches full charge. The mathematical relationship governing the charging process is given by the equation: V(t) = V_max * (1 - e^(-t / (R * C))), where V(t) is the voltage across the capacitor at time t, V_max is the maximum applied voltage, R is the resistance, and C is the capacitance.
RC Discharging Circuit:
This circuit configuration also involves a resistor and a capacitor, but in this case, the capacitor is initially charged and then allowed to discharge through the resistor. When the circuit is connected, the capacitor starts discharging, and the voltage across it decreases exponentially. The discharge process also follows an exponential decay, and the mathematical relationship is given by the equation: V(t) = V_initial * e^(-t / (R * C)), where V_initial is the initial voltage across the capacitor.
RC Low-Pass Filter:
An RC circuit can also be used as a low-pass filter. When a sine wave or any other input signal is applied to the circuit, the capacitor allows lower frequencies to pass through while attenuating higher frequencies. This is because at low frequencies, the capacitor has time to charge and allows more current to pass through the resistor, while at high frequencies, the capacitor doesn't have enough time to charge and impedance becomes higher.
RC High-Pass Filter:
In this configuration, the resistor and capacitor are connected in series, but the output is taken across the capacitor. This setup allows higher frequencies to pass through while attenuating lower frequencies. At higher frequencies, the capacitor's impedance becomes lower, allowing more current to pass through it, while at lower frequencies, the impedance of the capacitor increases.
These are some of the fundamental circuit configurations involving only capacitance (C) and resistance (R). They have various applications in electronics, signal processing, and control systems.