When you connect a resistor across an AC (alternating current) source, it affects the amplitude of the output waveform but does not change the frequency.
The primary function of a resistor is to limit the flow of current in a circuit by impeding the flow of electrons. In an AC circuit, the resistor offers resistance to the alternating current flow. As a result, the presence of a resistor causes a voltage drop across it, according to Ohm's law (V = I * R), where V is the voltage drop, I is the current, and R is the resistance.
Since the resistor causes a voltage drop, it reduces the amplitude of the output waveform. The higher the resistance, the greater the voltage drop and the larger the reduction in amplitude.
However, the resistor does not impact the frequency of the AC waveform. The frequency is determined by the characteristics of the AC source itself, such as the generator or power supply. A resistor simply responds to the voltage and current provided by the AC source.
It's important to note that when analyzing AC circuits, the behavior of resistors alone may not be sufficient. The presence of inductors and capacitors, which introduce reactance to the circuit, can significantly impact the overall behavior, including frequency response and phase relationships.