How do capacitors work on a circuit?

Question

I’ve tried to figure this one out, and honestly, there are a lot of good articles and videos out there trying to simplify and explain how certain electronic components work but they *still* get too technical and jargon-y. Like, what’s the actual for capacitors?

In: 4

Answer 1

Capacitors store a little bit of electric charge.

The key concept that makes capacitors useful in circuits is the *rate over time* at which capacitors store and release this charge can be controlled with resistance (using resistors).

This gives control over the rate at which the flow of electricity changes.

For instance, some audio circuits are susceptible to noise, near-instantaneous fluctuations in voltage that sound like hissing in your speakers. Tapping the connection with a resistor and capacitor that lead to ground absorbs the voltage fluctuations and smooths out the remaining signal, eliminating the noise.

Because capacitors store charge over time, when combined with a transistor, they can control timing. A transistor controls flow of a large current based on the voltage at its gate. Using a capacitor, you can control how long it takes for a voltage to reach the transistor’s gate threshold (voltage at which current begins flowing through the transistor) which can be used to make the transistor create regular pulses of current.

Even more useful is when you add an inductor to a circuit with a resistor and a capacitor. An inductor gives electricity inertia, which keeps current flowing in a particular direction for a short period of time. When you combine an inductor and a capacitor, current flow in one direction is sustained by the inductor, decreasing as the capacitor charges and pushes back against the incoming electricity. When the capacitor is full, current flow stops, then reverses back through the inductor in the other direction. If the outgoing current is led back to the other side of the capacitor, the circuit oscillates as the current flows back and forth between each side of the capacitor. This creates alternating current, which is essential in many applications such as radio and audio circuits.

In short, capacitors allow the engineer to precisely control a circuit’s dynamic behaviour. When combined with transistors, they enable pulsing behaviour. When combined with inductors, they enable oscillatory behaviour.