Final answer:
The capacitive reactance of a capacitor is determined by the frequency of the AC voltage source, measured in hertz (Hz). It is calculated using the formula Xc = 1/(2πfC), and is inversely proportional to the frequency and capacitance.
Step-by-step explanation:
The factor that determines the capacitive reactance of a capacitor and is measured in hertz (Hz) is the frequency of the alternating current (AC) voltage source. The formula for calculating capacitive reactance (XC) is given by XC = 1/(2πfC), where f is the frequency in hertz and C is the capacitance in farads. The reactance is inversely proportional to both the frequency and the capacitance; thus, as the frequency increases, the capacitive reactance decreases, and as the capacitance increases, the reactance also decreases. It's important to note that while resistance in a DC circuit dissipates energy, capacitive reactance in an AC circuit does not; a capacitor stores and discharges electric energy, while providing opposition to the change in current, which is characterized by a 90° phase angle between the current and voltage.