Inductors exhibit different behaviors towards DC and AC due to their fundamental properties of inductance and reactance:

- Why does DC pass through an inductor? Inductors allow DC (Direct Current) to pass through them because DC represents a steady flow of current with a constant polarity. When DC is applied to an inductor, it initially behaves like a short circuit due to its low impedance at DC. As a result, the inductor allows DC to flow through it with minimal opposition, primarily resisting changes in the current.
- Why does a pure inductor pass DC and block AC of high frequency? A pure inductor, characterized by its inductance without significant resistance or capacitance, passes DC while blocking AC of high frequency. This behavior stems from the inductor’s reactance, which is frequency-dependent. At low frequencies (like DC), the inductor’s reactance is low, allowing current to flow. However, at high frequencies (such as those found in AC signals), the inductor’s reactance increases, effectively blocking the flow of AC by presenting a high impedance path.
- Why can’t AC flow through an inductor? AC cannot flow through an inductor at high frequencies because of the inductive reactance. Inductive reactance XLX_LXL is given by the formula XL=2πfLX_L = 2 \pi f LXL=2πfL, where fff is the frequency of the AC signal and LLL is the inductance of the coil. As the frequency of the AC signal increases, the reactance of the inductor increases proportionally. This high reactance impedes the flow of AC current through the inductor, effectively blocking AC signals.
- Can an inductor bypass both AC and DC? No, an inductor cannot bypass both AC and DC simultaneously in the same circuit. Inductors behave differently depending on the frequency of the current passing through them. They allow DC to pass through with minimal impedance but block AC of high frequency due to the increasing inductive reactance at higher frequencies. Therefore, in practical circuits, inductors are used to either filter out AC signals or allow DC to pass through, depending on the design requirements and frequency characteristics of the circuit.

These principles highlight how inductors selectively pass or block currents based on their frequency, making them essential components in electronic circuits for filtering, energy storage, and signal processing applications.