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Q.
Filters are used alongwith a full-wave rectifier to
Semiconductor Electronics: Materials Devices and Simple Circuits
Solution:
To get steady $DC$ output from the pulsating voltage normally, a capacitor is connected across the output terminals (parallel to the load $R_{L}$ ).
One can also use an inductor in series with $R_{L}$ for the same purpose.
Since, these additional circuits appear to filter out the $AC$ ripple and give a pure $DC$ voltage, so they are called filters.