Hertz, abbreviated Hz, is often used to describe the operating frequency of electronic devices. A Hertz number can be found on LCD televisions, computer processors and cell phones. In general, the larger the Hertz number, the faster the electronic device processes data.
In AC, or alternating current, electricity travels in a rising and falling pattern called a "sinusoidal" waveform. The term "sinusoidal" means that the waveform takes the shape of the sine function in Trigonometry, which looks like a sideways "S." The AC waveform ascends to a positive peak and descends to a lower peak, repeatedly. It takes time for the electricity to "peak," and that is why the waveform gets a smooth, rounded shape. For example, household electricity travels in a sinusoidal waveform with peaks of +120V and -120V.
In DC, or direct current, electricity is naturally at flat level and does not alternate between positive and negative peaks. DC electricity is used in digital electronics, and sometimes artificial waveforms are created. When that occurs, the waveform behaves like the AC, sinusoidal wave. The difference is that the digital waveform has flat levels instead of rounded peaks, and it alternates between +5V and 0V. The DC, digital waveform takes on a "square" appearance and is often called a square wave.
A waveform of AC or DC electricity is comprised of a repeated string of positive/high and negative/low peaks. A single peak-to-peak alternation is called a wave period or a wave cycle. A wave cycle can be observed and measured on a laboratory tool called an oscilloscope. The amount of time that it takes one wave cycle to occur indicates the frequency of the wave.
Hertz and Frequency
Hertz is the number of waveform cycles per second. For example, household electricity travels at a frequency of 60 Hz. This means that 60 cycles of +120 to -120V alternations are traveling through household wires every second. Hertz is the standard unit that is used to measure frequency in all scientific disciplines.
120 Hz Vs. 240 Hz
To demonstrate the concept, a 120 Hz LCD television has a screen that "reacts" to incoming video data at a speed of 120 times-per-second. This indicates the quality and clarity of the picture. A 240 Hz television has a screen that reacts 240 times-per-second to incoming video data. Because 240 Hz is faster than 120 Hz, the 240 Hz television will produce a clearer picture and will be able to react to a larger amount of incoming data, such as the data in a high-definition signal.