# Eli5: What does the frequency (Hz) have to do with electrical output? If the world has 50/60 Hz frequency for their outlets, what exactly does that mean/do? Is it as simple as if it goes below/exceeds the specified frequency it just gives/reduces power output or something different?

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Eli5: What does the frequency (Hz) have to do with electrical output? If the world has 50/60 Hz frequency for their outlets, what exactly does that mean/do? Is it as simple as if it goes below/exceeds the specified frequency it just gives/reduces power output or something different?

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The Hz tells you the frequency that the Alternating Current is alternating at. Think of DC current as a constant push, while AC current is going “push, pull, push, pull, etc.” very quickly. Something like an incandescent lightbulb probably doesn’t care too much what frequency current it’s getting, but something like your laptop has to convert that AC into DC for the computer to use. Feeding it the wrong frequency would likely break something very quickly.

Hertz is just a measure of how many times something happens per second. In the case of electricity, Hertz is referring to the amount of times every second that the current changes direction back and forth in an alternating current. eg. 50 Hz = 50 changes per second.

From my knowledge Alternating current is used because the alternative, Direct Current, doesn’t work in transformers which means the national grid can’t change the voltage of the power, so it’s inefficient due to the heat generated from cables at a high current.

Alternating current must be at specifically 50Hz or 60Hz, or whatever the standard is because appliances are made for specific Hz’ will often be damaged if the wrong Hertz is used.

Most of the power in the electrical lines is made by generators, which are big wheels being spun around, and as they spin, they use magnets to create electricity. Because of the spinning, this electricity also goes up and down, at a rate related to the speed of the turbine. If you were to put a voltmeter between the two sockets of your power outlet, you would see a wave that goes up and down 50 or 60 times a second (tip: don’t do this, it could be dangerous, especially in a country with 220V power).

For the most part, this frequency doesn’t *do* anything, it’s just an property of the electricity.

If it were to go above or below the frequency, it **would** impart a slightly different amount of energy, but mostly what it would do is damage electronics. Most consumer electronics wouldn’t mind much (and you can see this is things like cell phone chargers that work at 50Hz **or** 60Hz, or light bulbs, or…), but all the transformers and stuff along the way carrying thousands of volts and thousands of amps are more finely tuned, and can take damage if the frequency drifts too much. High-power house appliances like washing machines and dryers could also be problematic.

Most power systems call for the frequency to be maintained to within 1% Hz – so from 49.5-50.5 Hz or 59.4-60.6 Hz. What precisely causes the frequency to drift is actually incredibly interesting and somewhat beyond ELI5 range, but basically, when there’s more demand than supply, the frequency goes down, and when there’s more supply than demand, it goes up – but it’s the difference in supply and demand that changes the frequency, not the frequency changing anything.

tl;dr if the frequency drifts too much, it can break stuff, but otherwise it’s mostly just a standard

Not that simple. There are basically two kinds of ways to supply electricity “Direct Current” which is just a constant flow of electricity, we’d get this from batteries. And “Alternating Current” which just sort of *shakes* electrons back and forth really quickly, this is what we get from our wall outlets. The frequency refers to how the electrons shake, back and forth 50-60 times per second.

In general Alternating Current is best for long distance power delivery which is why we use it in our homes and outlets. Direct current is great, but only good for small distances, like the batteries in your phone. Going from one to the other requires special electrical devices.

In terms of frequency it’s important for a few reasons – the two big ones

1. You can’t mix frequencies, you have to chose one and stick with it. In a sense choosing 60 hz is arbitrary, different countries use different standards.
2. It does affect how certain devices work, like electrical motors and lights and things, so while there are some benefits to choosing a specific frequency (it’s not completely arbitrary) but you’ll end up designing the devices to the standard. That makes changing the standard a pain in the tush, like the US going metric, it’s just not worth the hassle.

Fun Fact – you can *hear* the 60 hz frequency if you play guitar! Since guitar pick ups turn frequency into notes on the amplifier they will “hear” the 60 frequency as what they call the “60 cycle hum”. It’s that MMMMMMMMMM you hear when you plug a guitar in. In order to cancel that they developed a pick up that loops back against itself, sort of like doing a +60-60=0 thing. That pick up is called a “humbucker” for this reason, and it’s doesn’t have the hum.

Some devices have electrical motors that are designed for AC current, and they basically “expect” the power outlet to have the correct frequency too, not just the correct voltage and current. Clothes washer, dryer, dishwasher, etc, these would be examples where the motor is AC rather than DC.