Hey, there, guys. Paul here from TheEngineeringMindset.com. In this video, we're going
to be discussing voltage. We'll learn what is voltage
and potential difference, how to measure voltage, the
difference between direct and alternating voltage
as well as current, and finally, we'll briefly look at why and how voltages vary around the world. In our last video, we learned
that electricity is the flow of free electrons between atoms. Voltage is what pushes the free
electrons around a circuit. Without voltage, the free
electrons will move around between atoms but they
move around randomly, so they aren't much use to us. It's only when we apply
a voltage to a circuit that the free electrons will
all move in the same direction, causing current. It's easy to imagine voltage
like pressure in a water pipe. If we have a water tank
completely filled with water, then the mass of all that water is going to cause a huge amount of
pressure at the end of the pipe. If we have a water tank
that's only partly filled, then there will be much
less pressure in the pipe. If we open the valve
to let the water flow, then more water will flow at a faster rate from the high-pressure tank compared to the low-pressure tank. The same with electricity;
the more voltage we have, then the more current can flow. Voltage can exist without current. For example, we can measure
the pressure in the pipe with the valve shut with no water flowing, and from this, we can tell
that the pipe is pressurized. What we're really measuring
is the pressure difference between what's inside the pipe compared to the pressure outside. The same thing if we
have a battery connected to a circuit with an open switch. The voltage is still
present, we can measure that, and as soon as the switch closes, it's going to push the free
electrons around the circuit. We sometimes hear voltage referred to as potential difference. This really means how much
work can potentially be done by a circuit. Coming back to our water analogy, if we have two lakes at the same level, then there is no potential to do work because the water isn't flowing, but if we raise one lake
higher than the other, then this higher lake
now has the potential to flow down to the second one, and if we give it a
path, then it will flow. If we place a turbine in its path, then we can use its
energy to power a light or even an entire town. Back to the electrical circuit, this battery has a potential difference of 1.5 volts between its
negative and positive terminal. If we connect a piece of wire to both terminals of a battery, then the pressure of the
battery will force electrons to flow all in the same
direction, along the same path. We can then place electrical
components in the path of these electrons to do work for us. For example, if we place
a lamp into the circuit, then this will light up as
the electrons flow through it. If we then added another battery
to the circuit in series, then the electrons will
effectively be boosted by my second battery
because they can only flow along this path, and there
is more energy being added. This will combine the
voltages so we get 3 volts. More volts equals more pressure, which means more pushing force. That will mean more electrons will flow and the lamp will glow brighter. However, if we were to move the battery and connect it in parallel, then the path of the electron splits. Some will flow to the first battery and some will flow to the second battery, therefore, the batteries will
both provide the same amount of energy, so the voltage isn't combined, the voltage isn't boosted,
and we only get 1.5 volts. So, the workload is split by the batteries and the lamp will be powered for longer, but it will be dimmer. We've covered this in much more detail within our Electrical Circuit series. Do check that out, links are
in the video description below. We measure the potential
difference of voltage with the units of volts,
and we use the symbol of a capital V to show this. If you look on your electrical appliances, you will see a number next to a capital V, indicating how many volts
the product is designed for. In this example, the manufacturers of this USB hard drive are telling us that the device needs to be connected to a five-volt DC, or
direct current supply and it needs one amp of
current for the device to work. The term volt comes from
an Italian physicist named Alessandro Volta, who
invented the voltaic pile, which was the first electrical battery that could provide an electrical current in a steady rate in a circuit. Voltage and volts are different. Remember, voltage is the pressure and volts is just the units
we use to measure it in. The same as we know the pipe has pressure but we use units to measure this pressure, such as bar, PSI, kPa, et cetera. As we saw earlier, we can
measure volts with a voltmeter. This can be separate or
part of a multimeter. If you don't have a multimeter yet, you can pick one of
these up really cheaply. I highly encourage you to
have one in your tool kit. I will leave a link in the
video description down below for where to get one for a good price. To measure voltage, we have to connect to the circuit in parallel
across the two points we would like to know the voltage, or potential difference, for. So, for a single battery in a circuit, then we measure 1.5
volts across the battery and we also measure 1.5
volts across the lamp. The battery is providing
providing 1.5 volts to the lamp, and the lamp uses 1.5 volts
to produce light and heat. In a two-lamp series circuit, we measure 1.5 volts across the battery, 1.5 volts across the two lamps combined, but 0.75 volts across
the lamps individually. The voltage, or potential, has
been shared between the lamps to both provide light and heat. The lamps are dimmer because
the voltage has been shared or divided. Again, we'll cover this in more detail in our Electrical Circuits Tutorials. So, we saw earlier that voltage
and volts are different. Voltage is pressure and volts
is the unit of measurement. So, what does one volt mean? One volt is required to drive one coulomb, or approximately 6 quintillion,
242 quadrillion electrons, through a resistance of
one ohm in one second. That's still a little confusing, so another way to explain this is that, to power this 1.5-watt lamp with a 1.5-volt battery
would require one coulomb, or 6 quintillion,242
quadrillion electrons, to flow from the battery and
through the lamp every second for it to stay on. To power this 0.3-watt lamp with a 1.5-volt battery
would require 0.2 coulombs, approx 1 quintillion,872
quadrillion,600 trillion electrons to flow from the battery and
through the lamp every second for it to stay on. If we try to use a lower
voltage, the lamp would turn on but it decreases in brightness
as the voltage decreases. That's because there is less pressure to force electrons through it. Less electrons flowing, less
light that can be produced. The lamps are only rated for
a certain voltage and current. If we use a higher voltage, then the lamp will become brighter because more electrons
are flowing through it, but if we add too much
voltage and current, then the lamp will blow because
too many electrons tried to pass through at once. If we look at some typical batteries, we can see that this AA battery
has a voltage of 1.5 volts, and this one has a voltage of 9 volts. These are sources of direct voltage, meaning, the pressure it
provides moves the electrons in a constant current in one direction, much like the flow of water down a river. We cover this in our last
video on electricity basics, so do check that out
if you haven't already. Links are in the video description below. Direct voltage is usually
represented with a capital V, with some dots above this
and a small horizontal line. You can see an example
of this on the multimeter for the setting we would need in order to measure the
voltage in a DC supply. If we plotted this voltage against time, it would produce a straight
line because it is constant; it is direct in one direction. The voltage in our wall
sockets is alternating voltage. This is a different type of electricity. In this type, the electrons alternate between flowing forwards and backwards because the polarity of
the circuit is changing, much like the tide of the sea. If we plotted this voltage against time, we would get a sine wave
as it moves forwards and rises to its maximum
and then starts to decline. It passes through zero,
and now the current is flowing backwards but
it then hits its minimum and reverses direction again. This is usually represented
with a capital V with a wave line above it. You can see that on the
multimeter here, also, for measuring AC voltage. The voltage at these
sockets varies depending on where in the world we are. The majority of the world
uses 220 to 240 volts, but North, Central, and
some of South America, as well as a few countries scattered across the planet
will use 110 to 127 volts. We can measure the voltage at our sockets and see that it actually changes
slightly throughout the day as the demand on
electricity network varies, and we can do that using one
of these cheap energy meters. Again, links in the video
description down below. If you want one of these, you can pick them up fairly cheaply, and they're a great
device for your toolbox. The reason for different
voltages around the world goes all the way back to the beginning, when electricity first
started being distributed. At first, there was no standardization, so each distribution
network had it's own voltage and frequency for whatever
their engineers felt was best. Eventually, over time, some companies grew and dominated the market, and so voltage and frequency standardized
as their products and services expanded. Governments also had to
step in and pass laws and regulations to help
standardize their countries so that people could buy products easily but also trade products
with other countries. This is still a problem to this day, but it's pretty much too late to fix, as everyone is now so reliant
on their electrical devices and we would need to
replace or modify them all to solve the problem. For example, if we take a
hair dryer from the U.S., which is rated at 110 volts, and we plug it into a
wall socket in Europe, which has 220 volts, the
hairdryer will burn out at full power because there is
just simply too much voltage, or too much pressure, and
the device just can't cope. If we took a hair dryer from Europe and plugged it into a U.S. socket, it probably won't turn on, but if it does, it's not going to be very
strong; it's gonna be pretty weak because there just isn't enough
pressure for it to function. Some products can be used in
different voltages, though. You need to check the
manufacturer's labels on the product to first see if the
product has been designed to cope with different voltages. For example, this laptop charger shows that it can be used on voltages
between 100 and 240 volts, whereas this charger is only rated for 220 volts or 240 volts. Okay, guys, that's it for this video, but if you want to continue your learning with your electrical engineering, then check out these videos here and I'll catch you there
for the next lesson. Leave your questions in the
Comment section down below, and don't forget to follow us on Facebook, Instagram, Twitter, as well
as TheEngineeringMindset.com. Once again, thanks for watching.
