Difference between AC and DC Current Explained | AddOhms #5


If you’re looking for a video on
legendary rock music you might have found the wrong channel. On a previous Add Ohms video we looked at Voltage, Power, and Current… …and you might remember this
animation. one problem with this animation is that the voltage source
shown was an AC source while the current flow was shown as DC So let’s talk about
the difference between AC and DC. The letters DC stand for Direct Current and it generally means the electrons flow in a single direction. AC stands for alternating current and it means that the flow of electrons change. Now, this is where things can start to get a little confusing. This is an AC voltage source
so it’s both AC and voltage. How can voltage and current be the
same? Well it turns out we tend to use AC and DC abbreviations for voltage, as well as, current. So in other words AC voltage, or current, is voltage, or current,
that changes. DC voltage, or current, is voltage, or current, that is steady. Okay, so let’s take a little bit closer
look at these two starting with DC Check out this AA, or LR6, battery. It provides 1.5 volts. This example circuit is going to
be a DC motor like you might find in a toy car. When we insert the battery into
the circuit, current begins to flow in a single direction, turning the motor. If we drew a graph, where the vertical axis is voltage and the horizontal axis is time, we can see that the voltage at this point stays constant. Now, since this is a battery, eventually,
it’s going to run out energy; and its output voltage will drop. So we know that the voltage will change over time, but the polarity will stay the same. So what is polarity? Well polarity defines the positive
direction and for a battery the positive voltage is created from the positive
terminal. So… what would happen if
we turn this battery around? Well, that reverses the polarity which means the current will flow in the
opposite direction as before, causing our motor to spin in the opposite direction. Okay, so let’s move on to AC and in this case we’re going to use a light bulb and a North-American AC socket, because well, I live in North America! Notice how the circuit behaves when we turn the switch on. Let’s break down what we’re seeing by using the voltage graph again. Notice how the current is flowing
in one direction and as voltage increases the light bulb gets brighter.
Once the voltage reaches its peak current flow stays the same but the
voltage begins to drop and the light bulb gets dimmer. Once we reach zero volts,
the voltages polarity changes causing current to flow in the
opposite direction, and again as the voltage gets closer to its peak the bulb gets
brighter and then dims back down. Okay we needed to define a couple of things. First, is the change from start to finish is called a cycle. The rate at which the
cycle repeats is frequency. Now frequency is measured using the unit “Hertz,”
which means cycles per second. Different parts of the world use different frequencies for their AC systems and it can either be 50 or 60 Hertz. What this means is in one second
the cycle repeat itself at least 50 times. Believe it, or not, incandescent bulbs are actually
flashing over 50 times per second! Now it turns out, that this rate is so fast that our slow human eyes sees it as
constant light! In summary, while the abbreviations for AC and DC include the word “current,”
they can be used to describe different types of voltage and current. DC voltages do not fluctuate while
DC current flows in one direction AC voltages change over
time and the current flow can alternate direction. If you have questions about this video please
feel free to leave comments below. For more electronics tutorials
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100 thoughts on “Difference between AC and DC Current Explained | AddOhms #5

  1. I think you are wrong when you said the current is going out from the +. The electrons are actually going from the – to the + (like a magnet)

  2. Question: Why would i use or what situation would require an AC current insread of a DC?

    Are LED's fed with a DC because of the Diode?

    Literally have no one in my life right now to answer that question for me….

    Thanks for this great video, better education than my 3 years course. No Joking.

  3. I'm still a bit confused. Does the current come from the live wire and then from the neutral wire then again from live, so on and so forth?

  4. I'm working on equipment and my power supply is supposed to be outputting -12vDC, but it's fluctuating between -5V and -12v. What's wrong?

  5. how can you determine if an appliance is ac or dc without knowing the current? and how can the electrons with ac be kept charged when they don’t travel past the power source anymore?

  6. As i was watching this video, i decided to take out my phone with super slow mo (960fps) and record my hand moving next to light bulb. Indeed you can see lightbulb going on and off while its slow mo. Thanks so much for this!

  7. So here is something I'm fundamentally confused about with home wiring. Home wiring is AC, but if you are replacing a socket or switch, you connect two wires, but only one is "hot". If you put a continuity tester next to the hot wire it lights up, but it doesn't light up if you put it next to the other wire. To me this seems like the current is flowing in on direction. If the current direction is constantly alternating wouldn't both wires be "hot"?

  8. Please explain "Earth" which is said to be tied to Neutral (Mains 240 Volts 50 Hz), in the UK : if that AC causes it to become Positive…. Argh!!!

  9. I wish you ware may teacher, straight and simple to point. Have known DC, AC and hertz.what makes battery positive and negative terminal

  10. Great work! Is this why monitor screens and light bulbs hooked up to an AC power source appear to be fluctuating in intensity in certain video recordings?

  11. "Believe it or not incandescent bulbs are flashing over 50 times per second" ?

    Since there are two zero-volt intercepts in a single cycle, with a frequency of 50 hz there are at least 100 flashes in an AC current not 50. Right?

  12. So if you had a high speed camera watching a light bulb, would you see frames where the bulb is turned off, or at least significantly dimmer?

  13. Do incandescent bulbs really flash? I get that the voltage is doled out in tiny increments, but does the filament have time to cool down enough to darken in-between?

  14. only real explanation of "direct" and "alternating" out there. wikipedia and quora couldnt handle this, cant explain invisible things without an animaton, thanks!

  15. Ok, but the bulb brightens and dims at 2x the frequency of the electrical power, so either 100 Hz or 120Hz.

  16. Hey, so I am looking into converting my car into an electric car. i did some research in on Tesla Model S and found that they convert DC (Battery Packs) to AC. Does that just mean that the AC will provide more energy when trying to turn the drive shaft? how does DC and AC compare on voltage output i guess?

  17. but surely (in ac) this means that the electrons wont actually go anywhere if they are moving back and forth

  18. I disagree with that a bulb flashes at 60hzbecause the tungsten filament takes time to cool off from it's glowing state, pulses yes but it's not a secret dance party.

  19. Why does the change in direction go together with the voltage dropping to zero in the middle? Why can't the change be without any drop in voltage?
    Why do the electrons flow at all with AC, if they get pushed back and forth 50 times a second? If I were to suck and blow water through a tube 50 times a second, nothing would come out on either end.

  20. Since AC flows both directions, how do power companies calculate electricity used? Does AC actually flow past a given load and return back to the original source? like DC?

  21. Hello AddOhms. I wanted to ask if the light bulb with the AC current also lights up when its voltage is negative. In other words does a light bulb light up if its current and voltage is reversed as in AC currents? Or do they wait for the Voltage to be in their preferred direction again?

  22. I have one point of confusion. When drawing the V vs Time graph for AC you say that the voltage increases and then decreases. But you say that the current stays the same.

    Since V=IR how is this possible?

  23. Okay so we know what the differences are but what are the benefits. Why would anybody ever use AC? That's what I was hoping to find out

  24. Awesome! Can you please explain what’s the input & output voltage range specified in devices? I saw a led driver that says 9 to 24v DC input but 30 to 38v DC output. What does that mean please 😳

  25. Great video, thank you. What are the advantages and disadvantages of each current type? It seems like DC would be a better, more efficient and straight forward choice, no?

  26. I used to work as a caregiver for adults with autism, I found out that some people are sensitive to incandescent lights. They explained it to me as if the lights were blinking, this sums it up pretty it well.

  27. Ive been watching a lot of tech related videos lately and every time a battery they show that electricity flows through the negative end and some videos show that electricity flows through the positive end can someone tell me what end of the battery electricity flows through? Thanks

  28. Just a side note from my picky self, human eyes aren't slow, they can easily see an image flashed for 1/120th of a second. XD
    But it is amazing that our lights flash like that without our noticing

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