Ham Radio General Class Practice Test

What is the output waveform of an unfiltered full-wave rectifier connected to a resistive load?

1. A series of DC pulses at twice the frequency of the AC input

2. A series of DC pulses at the same frequency as the AC input

3. A sine wave at half the frequency of the AC input

4. A steady DC voltage

The correct answer is: A series of DC pulses at twice the frequency of the AC input

The output waveform of an unfiltered full-wave rectifier connected to a resistive load produces a series of DC pulses at twice the frequency of the AC input. This occurs because a full-wave rectifier processes both halves of the AC waveform, effectively reversing the negative half-cycle so that both halves contribute positively to the output. As a result, for each complete cycle of the AC input, the rectifier generates two pulses of output—one for each half of the waveform. Therefore, if the AC input frequency is, for example, 60 Hz, the output frequency after full-wave rectification will be 120 Hz, which is twice the original frequency. In contrast, a series of DC pulses at the same frequency as the AC input would be characteristic of a half-wave rectifier, which only utilizes one half of the AC cycle. A sine wave at half the frequency of the AC input does not represent any form of rectification and would not occur in this context. A steady DC voltage could only be obtained through further filtering of the output waveform, such as using capacitors to smooth the waveform, which is not the case in an unfiltered scenario.