Name: Why Use AC Instead of DC at Home??
Uploaded: 2021-07-18T16:56:30.000Z
Duration: 10 min 36 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Transition words & phrases

Hi. Why do we ever use AC to power homes instead of DC?

Adverbs of manner

Haven't I showed you that AC is typically more dangerous than DC?

Yes! In fact pretty much every device at home has to rectify AC into DC

first before it can use it so why? Why am I angry?

The reason is elementary. Once there was a fight between a guy named Nikola Tesla being AC and Thomas Edison

being DC and Tesla won the contract on his employer Westinghouse company to provide power with AC

no matter how hard Thomas Edison tried to expose the dangerous nature of AC by

electrocuting dogs and elephants in public.

Now I remember why I'm angry; this Edison guy was an animal! He even invented the electric chair to execute with AC

--not because it was a cleaner or better way to execute--because he wanted to deface AC by forever associating it with death.

Nikola Tesla very rightfully won this battle.

Yes, AC can be more dangerous than the same level DC but a higher level DC can be as dangerous

if not more and just because something is dangerous

we don't stop using them like for example if you live in a high-rise

you are not in a constant risk of jumping off the window. But is there an advantage of using AC?

I mean, back then all they wanted was light using incandescent lights and those don't care about AC or DC.

Here I'm running a regular light bulb on AC as usual

Anyways with this I'm converting the AC into DC using

It's a single diode, but it will do and if I measure the voltage at the output

170 volt DC and although it's still quite dangerous

I can still touch it and it's not as remotely as painful as touching the 120 volt AC

And it's even a little brighter because it's 170 volt continues

Beside the lights the electric motors were becoming more popular in home

Appliances like meat grinders or fans and such, but even those could be made into brushless

AC or brushed DC for example, of course a brushless AC motor like this one that I took from an old

microwave oven can last much longer than a brushed DC...

Loose wires, avoid them anyways brushes in DC brushed motors wear out eventually

And that's why AC motors can last longer, but beside that fact there doesn't seem to be much preference between AC and DC

But the real advantage of AC is not at home

It's before electricity even gets to home in transmission lines

And that's why Edison's DC power distribution system eventually died away, here

I made a transmission line using thin wires and using my supply

I'll try to place 10 volts across my 1 ohm load for 10 amps of current

And I'm measuring the voltage across my load. Let's try it

Transmission line is starting to smoke and heat up and the voltage continues to drop see the line resistance is so much that the voltage

Across the load doesn't even get to ten volts

It's at seven volts for seven amps through the load and because of the high resistance. It's heating up so much

Similarly because Edison was passing low voltage across the transmission lines a ton of current was passing through the lines

And there is a limitation to how thick you can make the wires before they break under their own weight or become too expensive

Huge currents through the resistance of the wire would result in large voltage drops over longer distances

And that's why Edison's system could only transmit power to around a mile or two from the power source

Otherwise the power loss would be so much over the lines

That would cause huge inefficiency, of course Edison was aware of his s**tty system

So he decided to let one of his genius employees to take care of the problem, who was our beloved Nikola Tesla

He was working for Edison at the time. according to Tesla Edison promised him

$50,000 which was a lot of money back then, if Tesla was able to make great improvements to Edison's DC system

Which Tesla did in a few months and when he went to Edison to ask for the money?

He said "Haha. I was joking obviously you're not aware of our

American humor," which Tesla said  "F*** you, I quit !!!"

Later Tesla came up with his genius system and developed it for Westinghouse company

What he did was to transmit power much smarter. He used AC so he could change the voltage level using transformers, here

I'll use my auto transformer to generate 10 volt AC which would result in 10 amp AC through my 1 ohm load

But before I send it through the transmission line, first

I'll step the voltage up using my microwave transformer

and then I would step the voltage down after the line if I had a transformer

Well, guess I can borrow the one from our microwave

F**k. They're using tamper proof screws to stop me

What they don't know is that nothing can stop me. They are just postponing the inevitable

I'll just take a picture of the wiring before I pull it out. I don't want to blow it up later

Ok, now we have both transformers connected. Let's do some voltage measurements before I connect the load. At the input

We have close to 10 volts so that's good. On the transmission line

We get around 190-200 volts. And at the output

Again we have close to 10 volts so that's pretty good. Now, let's connect a load

1.6 volts? That's garbage. What happened? The transmission line voltage

This is worse than the DC system. What's going on Tesla? Let's measure the transformer secondary winding resistance

There's too much drop over the large resistance of the secondary, so these transformers are not made for this purpose

That was a bad example. It doesn't matter. I'm gonna transmit power. No matter what

And our transmission line is not burning so that's always a plus

Nothing is exploding. What is the transmission line voltage now?

This is a pretty bad example, you can see that

I'm transmitting more power than the DC system