Volts, Amps, and Watts Explained

What's the difference between a volt, amp, and watt? Why is your power bill in kilowatt-hours and your battery bank in milliamp-hours? Why are there so many units?!

[justanotherguy]

I watch this video every 3 months, just to make sure i don’t forget the topic.

[QuikVidGuy]

as someone who failed chemistry, this answered about 4 questions and raised about 16

[HeyItsKora]

Never thought I’d end up on a Linus video when trying to understand my uni coursework xD

[hawk]

As someone who is in the process of becoming a science teacher. This is one of those videos that will be saved and used in classes later on.

[godfreypoon]

I think this explanation is a bit over-complicated... but can I do better? Here goes.

Volts (voltage) is kinda like water pressure.
Amps (current) is like how much water is flowing. Think current, as in the current flowing in a river.

Just like water, if there is no pressure, then the water won't flow.

If there is more _resistance_ (say, a river with many twists and turns, or a narrow water pipe), it will take more pressure to make the water flow. This is just the same as electrical resistance (which is measured in _ohms_).

Usually, if you have a source of electricity, it will be supplied at a certain voltage. Say, 120V or 240V. This voltage normally doesn't change much, regardless of what you plug in.

Depending on the _resistance_ of what you connect to it, a certain _current_ will flow. When you have both _voltage and current_, power is used. Power is measured in _watts_.

If you don't have anything plugged in, that is (more or less) a resistance of infinity. No current will flow. As you might guess, there is no power used.

If you short circuit your electricity supply, that's a very low resistance. Plenty of current will flow. Lots of power is used!

To carry lots of current, you will need thick copper in your wire. The electrons flow in the copper, so you need a thicker "pipe" if there is more flow.

If your supply is a high voltage, you will need thicker plastic insulation around the copper. Just like you need a thick walled pipe to keep lots of pressure from bursting out.


Perhaps you have a heater, which is 1, 200 watts, or, 1.2 kilo-watts (kW). This is how much power it will use.
Of course, your electricity bill will be higher if you have your heater switched on for longer. If you run it for 10 hours, you will have used 10 times as much energy as if you ran it for 1 hour.
This is why energy is measured in kilowatt-hours (kWh). That is, the number of kilowatts of power used, multiplied by the number of hours it was used for. Running your 1.2 kW heater for 10 hours will consume 12 kWh.

The expression "kilowatts per hour" does not make any sense (unless there is something very, very special going on!).


Batteries are slightly unusual, as they are measured in how much current they can provide, for a certain amount of time. This is because of chemical reasons. So, your battery may be able to provide 2 amps for an hour. This is a 2 amp-hour battery.
If the battery voltage remained exactly the same, this would equate to a certain amount of kilowatt-hours, but sadly the battery voltage drops somewhat as it runs flat. This makes it more complicated, so amp-hours is the preferred unit of measure.


Now for some maths:

Voltage = Current x Resistance (V = I x R)
Power = Voltage x Current (P = V x I)

An example - your 120V, 1.2kW heater.

How much current is flowing? Put those numbers into the second equation.
P = V x I
1, 200 = 120 x I
I = 10 amps. Easy!

What resistance is your heater? Put the numbers into the first equation.
V = I x R
120 = 10 x R
R = 12 ohms.

Let's plug your heater into 240V instead! How much current would it draw?
V = I x R
240 = I x 12
I = 20 amps. Twice as much!

How much power?
P = V x I
P = 240 x 20
P = 4, 800 watts! That's four times as much! This may be a surprise. Your heater will certainly blow up.




Did I do better at explaining it? Please let me know!

[JimnyVR]

I can control the brightness of the light in my fridge depending on what setting my oven is running at... which is nice

[sharonjohnson]

My light just turned on for the first time. I'm married to an electrician and this is the best I have ever heard. Now I can talk like him and I want my EFI plugs back and a sine wave power control to hook up my telescope and computer. Im sure you get this. No more watts for me . I need to see my currents at play and know if I'm rated in all areas to safely protect my 6, 000. Equipment. Your the best.

[guestIdk-nihb]

7 years later, this is really useful. Had to watch it twice lol. Thank you so much!

[whoopn]

As an Electrical Engineer, great job! Would've been so much easier to understand this concept with this video many many years ago

[bloogaming]

Volts=Caliber
Amps=Firerate
Watts=DPS
AH=Magazine
WH=Total damage

[jfdd]

I have watched a few videos on this subject and was always confused. This finally cleared it up.

One more analogy incase someone needs it.

If you think of a can of hairspray, volts would be the pressure in the can

If you press the nozzle down, the amps(current) would be the measure of how fast the hair spray comes out

Watts would be a measure of how much hairspray was used in total

[JoshKindhart]

Linus I've been following your channel for a while. I've watched many youtube channels trying to understand the concepts of voltage and amps. Some of them even used the water analogy. I almost gave up trying, until I saw your video. There's something about hearing it from the right person that makes it click on a persons brain. Thank you so much!

[alexanderbrown]

Been in school for 22 years and this is - by far - the best explanation of volts vs amps that I have heard. Thank you.

[CarstenSvendsen]

That last bit though. First time I've ever seen an off-shoot in a techquickie. And it was GOLDEN!

[MrNicePotato]

In physics terms:
Electricity is measured in units of charge
Voltage(V)=how much energy per charge
Amp(I)=how much charge per time
Wattage(P)=how much energy per time
Therefore P=V×I
Imagine electrons as trucks carrying energy.
High voltage means each truck carries a lot of energy.
High ampere count (current) means many truck passes through.

[mskafridi]

After 42 years I finally understands the difference between, Amps, Volts and Watts, Thank you Boss

[ToxisLT]

wait, so US also uses kilowatt hours? But.. but that's dirty metric system! I thought they have something like 3 arm lengths of electricity, or something along those lines, they used to measure things in body parts.

[LXenta]

My teachers did a poor job to get me interested in stuff i guess. Thank you Linus, Guru.

[starwarsmaniac]

Not gonna lie, this was hella confusing ahaha 😂. So many analogies, I just wanted to know what each thing actual represents.

[jimmyhaotran]

The reason why it is called KiloWattHours, is because when you multiply two things together you will have to multiply the units as well, like how you do with the area, 10m * 5m = 50m^2. So if your device is running 1k Watt (per hour), and you used it for 24 hours. 1k Watt * 24 h = 24kWatt * h. That is why we have to keep the hour included, else you wouldnt have known whether that number is your total usage or just a usage on a specific period. Hope it helps