What are the key features of a high pass and low pass RC filter circuit?

Question

with more focus to the low pass RC filter circuit.

How do they differ from each other? In what way?

What can be described from its graph of the gain versus frequency?

Answer 1

In any filter you have a source (voltage or current), the filter, and a load (resistor or 'open' circuit high impedance).

For a high pass filter, the C is in series with the source and the load, while the R is in parallel with the load.

For a low pass filter, the R is in series while the C is in parallel

The graph of an low pass RC filter is flat (at 1 volt, for example) from DC/low frequencies up to the cutoff frequency (Fc), where is drops by a factor of 10 volts/volt per every decade of frequency (factor of 10).  AT the Fc, the attenuation of the filter is 0.7071 volts.

The graph of a high pass filter is the opposite.  From very high frequencies, the voltage output is a horizontal line (at 1 volt).  At the Fc it is 0.7071 volts, and going toward zero frequency (DC) it drops at a rate of 10 volts/volt per decade of frequency.

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Answer 2

You already typed the answer.

A high pass filter passes frequencies above it's cutoff frequency and rejects those below.

A low pass filter passes frequencies below it's cutoff frequency and rejects those above.