# What is an intuitive definition of Hertz?

So I have been told that I have a 240V-250V supply at 50Hz.....

What does 50Hz mean and please give analogy if possible, I am new to this stuff

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The hertz is the unit of measure of frequency and it is defined as 1 Hz = 1 1/s. So it basically tells you that if a phenomena has a frequency of 50 Hz it will be repeated 50 times in a second. A mechanical example is the circolar motion: if the period to make a complete circle is 0.5 s than the frequency is 2 Hz.
In your example means that you have an alternate current generator that repeat the same signal 50 times in a second. In other words the function that describe the voltage repeat itself 50 times in a second.

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From your description it appears you are describing your house current, or one of them, and 240 VAC @50Hz is common in many parts of Europe.

It is difficult to give you a real world analogy so let me try just diving right in. Voltage at current, power, from a battery is DC or Direct Current. This basically meant that the terminal that is positive is ALWAYS positive and also is the negative terminal always negative. This means current will essentially flow in only one direction.

House current is most often AC, or Alternating Current. It pulses back and forth, changing voltage and direction in a pattern usually described as "sinusoidal" that is to say a gradual increase from zero "up" to the maximum voltage at the peak upon which it reverses and begins to drop back to zero and then through zero to the opposite polarity, again gradually rising (or falling, depending on your viewpoint) until it reaches an equal in amplitude but opposite in polarity peak, something like a mirror image of the first 180 degrees of swing.

The reason for having both types is each has it's advantages and disadvantages. The reason AC is used in homes is because it is most efficient and convenient in transmission lines because the pulsing allows for the employment of step-up and step-down transformers. Stepping up at the source of power allows for long distance transmission with minimal losses. Stepping down at sub-stations and again at your home (and often again within lower voltage appliances) reduces hazards and equipment size.

Hope this helps.