Period vs. Frequency: Understanding the Difference

Many alternating voltages and currents we encounter change periodically over time. This means their waveforms, whether voltage (V) or current (I), exhibit regular, repeating patterns. Think of it like a wave – it goes up and down, and then repeats that same up-and-down motion again and again as time moves forward. One complete up-and-down cycle is known as a “cycle”.

Frequency: How Often it Happens

Frequency essentially tells us how many of these cycles occur within a single second. It’s a measure of how quickly the waveform is repeating itself. The unit for frequency is called Hertz, abbreviated as Hz. You might have also heard it referred to as cycles per second, which is the same thing.

For instance, if a waveform completes 3 cycles in one second, we say its frequency is 3 Hz. A common example is the AC power supply in most countries, which has a frequency of 50 Hz. This means the waveform repeats itself 50 times every second.

Period: How Long a Cycle Lasts

Period, on the other hand, measures the time it takes for just one complete cycle to occur. It’s the duration of a single repetition of the wave.

Period and frequency are closely linked, and their relationship is defined by a simple equation:

Time Period = 1 / Frequency

Let’s use the 50 Hz power supply example again. If the frequency is 50 Hz, the period is 1/50 of a second, which is equal to 0.02 seconds. So, each cycle lasts for 0.02 seconds.

Amplitude: The Height of the Wave

While not directly related to period and frequency, it’s worth briefly mentioning amplitude. Amplitude, or peak value, refers to the maximum or minimum value of the alternating quantity (voltage or current). It’s essentially the “height” of the wave.

Different Frequency Ranges

We often categorize frequencies into different ranges based on their values:

• Audio Frequency: This refers to alternating currents with frequencies between 20 Hz and 20,000 Hz. These are the frequencies that we can typically hear.
• Radio Frequency: These are alternating currents with frequencies above 20,000 Hz (20 kHz). They’re used for things like radio transmissions and wireless communication.

We also use larger units of frequency, especially when dealing with high values:

• Kilohertz (kHz): 1 kHz = 10^3^ Hz (1,000 Hz)
• Megahertz (MHz): 1 MHz = 10^6^ Hz (1,000,000 Hz)
• Gigahertz (GHz): 1 GHz = 10^9^ Hz (1,000,000,000 Hz)

Converting Between Period and Frequency

Here are some handy calculators to help you convert between period and frequency:

Period to Frequency Conversion

Calculator-1:

• Period, ms (input):
• Frequency, Hz (Output):

Example #1:

• INPUTS: Period = 2 ms
• OUTPUTS: Frequency = 500 Hz

Frequency to Period Conversion

Calculator-2:

• Frequency, Hz (input):
• Period, ms (Output):

Example #2:

• INPUTS: Frequency = 1000 Hz
• OUTPUTS: Period = 1 ms

These calculators make it easy to switch back and forth between these two related concepts!