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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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.
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.
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.
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
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.
Think of it like a person pedaling on a bike. The 50/60 Hz is just how quickly they’re pedaling, it’s honestly pretty arbitrary how quickly they decide to pedal (well, it’s not for electricity, but the specifics of *why* a certain frequency is chosen is a bit complicated).
But in terms of the electrical grid, there isn’t just one person pedaling, it’s more like a tandem bike with a bunch of people pedaling. If one person were to attempt to pedal faster, they’d have to put in a lot of effort to speed everyone else up along with them. If they instead wanted to pedal slower, the pedals would outpace their feet and probably end up hurting them. So it is much more sensible for everyone to be pedaling at about the same speed.
We use AC power on the power lines. This is current that is generated in a way where it literally alternates between positive and negative voltages over time. That’s what 50Hz and 60Hz refer to: how many times per second the voltage alternates.
We chose to use AC for our power because it’s better at being transferred over long distances without losing a lot of energy. The physics behind this are weird and complicated but the main difference is if you run AC through a long wire you get “an electric field” and if you run DC through a long wire you have probably made “an electric heater”.
But DC is what almost all electronic devices need to run. There are devices that can convert AC to DC. The way this works is best if you can see how the electricity’s voltage changes on a graph, but there’s not a good way to do that on reddit.
A good AC electrical signal looks like a sine wave, go look that up on a search engine. You’ll see it’s a smooth curve between 0, some maximum positive value, 0 again, and some minimum negative value. In US households we are connected to power sources that alternate between +120 and -120V at a rate of 60Hz (I’m telling a small lie here that doesn’t matter in the big picture.)
The things that convert AC to DC tend to only deal with the positive part of that sine wave. So that means they only have any voltage at all for half of a second, and for most of that half of a second they don’t have the full power. So they rely on electrical components that sort of act like batteries, store the power from the wave, and release a smaller but steady voltage to the rest of the device. (A lot of the extra power ends up getting released as heat, which is why a lot of chargers and other devices get hot while in use!)
Using water as an analogy helps. Imagine you have a weird water supply that provides full-pressure water for 1 second, then no water for 1 second, and keeps going back and forth. That’s not great for brushing your teeth. But you can design a water tank that stores up the water and, after it fills up, provides you with a constant stream of pressurized water so long as you don’t try to use more than is being pumped in. That’s more or less what AC -> DC converters do.
But think about what happens if your water company suddenly changes the pattern after you design that system. If they add more time without water, your tank won’t stay as full and might not be able to give you a steady water flow for long enough to brush your teeth. If they add more time with pressurized water, your tank might get overfilled and any pressure relief valves you added won’t be sufficient. So it’s important the water company delivers exactly the rate of water they promise and don’t change their mind.
The same is true of DC -> AC converters. The cycle rate of the electricity affects how the power is converted, and having too slow or too fast of a cycle can either not work at all or give too much power to the device and damage it.
Some stuff in your house just uses AC power directly (most stuff with motors will.) The problem with changing the cycle is they’ll spin at different speeds based on how the cycle changed, a vacuum that spins too slow won’t work as well, and you can imagine trying to spin motors faster than they were designed to spin might not always end well.
> If the world has 50/60 Hz frequency for their outlets …
Nope, that’s not how it works. Some places, like the US, have 60Hz. Other places, like the EU have 50Hz. These frequencies are quite precise, not ±20%.
A device might say it requires 50/60Hz. That means it can take either, and possibly 55Hz but it’s not clear where you’d get that.
In most modern electronic equipment, the frequency isn’t important, as the alternating current is converted (rectified) to direct current, then converted to a high arbitrary frequency before being processed into the different voltages the device needs. (This is known as a switching power supply.) The application where frequency is most important is electric motors. A motor has a certain number of ‘poles’ which rotate it at a given speed for the design frequency. So a 60Hz motor will rotate slower if supplied with 50Hz. And as the frequency is different than what it was designed for, you could have overheating and other issues.
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