# Basic Electronics – Power Source

Power source! Power source is what makes all electrical system, equipment and devices come to life. As a hobbyist it is

very important to have a strong foundation on such concepts because

there is no such electric circuit or system that will run without it. To learn

more in detail what electrical power is, in this video we are going to talk about

the following. 1. What is electrical energy; 2. Why power source has two

terminals; 3. Components of power; 4. Types of power; 5. Examples of power

source; 6. Choosing the right power source for your application. [Music] Energy is the capacity to do work. Wait! I said I will make this easier right? So let’s

consider you as an example. Say you pick a bucket full of water and you walk

about 10 steps. It means you just created work, literally. Energy is the ability to

do work, if you have lots of it you have the ability to carry the bucket at very

long distances. This means also that, power in this example has two components the amount of strength you asserted and the height of the bucket is lifted. In an electrical system the power is you,

the electrical circuit is the bucket full of water and the total distance you

walk carrying the bucket multiplied by the power you exerted is what we call

energy. Power which has a unit of watts, is the

product of two components voltage and the current. Given by this formula P is

equal to V I, voltage as a unit of volts while current has a unit of amperes. Energy on the other hand is the product of power and time having watts-hour as

its unit. In other words energy is the measure of power delivered in a span of

time. To make it clear, suppose you have a washing machine rated 1500 watts and you operated it continuously for one hour. That means 1500 multiplied by 1, is equal

to 1500 watts-hour. If you’re going to convert it into kilo, a standard binary

prefix it’s going to be equal to 1.5 kilowatt-hour. To convert it into actual electric

consumption, suppose your electricity rate is 10 pesos per kilowatt hour, then

the cost of your electricity to run your washing machine in an hour is, 1.5 times

10 pesos that is equals to 15 pesos. So now you have already grasped what is

energy and power in electricity. In a nutshell, an electrical energy is the

amount of electrical power used in a specific span of time. Our electric

utility records our electricity consumption on a monthly basis and they do this by means of our electric meters. Since we already talked about energy and

power, let us learn how it is being connected into our electrical system,

device or equipment. Since we are just starting out let us

leave the three-phase system on a future discussion. Every power source has two terminals line 1 and line 2, and every appliance, machine,

equipment and devices, which we now refer to as “load” has two input terminal

as well. To know where to connect each wires of

the source and load, we will first consider the two types of power. The DC

or the direct current, and the AC or the alternating current.First off, the DC is the type of source where the voltage and current is steady

on a specific level all throughout a given time, it will not change. On the

other hand AC current is opposite to that of DC, as it is varying. Looking back at the graph you can see

that the DC shows a straight line, while the AC is a form of a wave which is

called a sinusoidal wave. It varies as time progresses, in an AC there is what

we call one “full cycle”, which is divided into a “positive half cycle” and “negative

half cycle”. The number of full cycles that occurs in one second is known as

frequency, which has a unit of Hertz. The most popular frequency is the 50 and

60 Hertz. Since DC flows steady, we can safely

assume that it flows in one direction. This is why DC source has its “polarity”. You cannot reverse the connection otherwise your load will not run or

operate, or in worst cases get burned. Meanwhile, in AC, since the flow of

current is varying. We can say that the flow of current changes direction in

every half cycle. This means that an AC system, you can interchange the

connection of the two terminals. So now let’s consider some examples of

the two types of power source. For the DC we have the battery, DC motor used as

generator, PV or solar panels and others. For the AC, the 100 or 240 volts wall

outlet, transformers and AC generators. Now let’s talk about how to choose the

right power source. In most electronic boards the supply is usually DC, whereas

for large applications such as motors, electric distribution network and

industries, AC is commonly used. Most equipment and devices specify the type

of source it needs and it cannot be changed if it’s AC, then use AC, if

it’s DC, use DC. However there is one aspect we can

manipulate assuming that it is the required type of power source. That is

power rating, voltage rating, and current rating To generalize the most common question regarding power source, let us consider

these three example questions. 1. Can i supply 100 watts to my device which is

rated 20 watts? 2. Can I use 220 volts supply with my device rated 110 volts? 3.

Can I use 10A supply to my device which is rated 50A? Let’s summarize our answer into these

three factors: 1. The supply voltage should be equal to the required voltage

of any load. 2. The load rated power should be 70% to

80% of the power supply rating. 3. Ampere rating of the load should not be larger

than that of the power source. So to answer those three questions. Can i supply 100 watt to my device which

is rated 20 watts? The answer is yes. Since power is the ability to do work,

by common sense the power source must have greater capacity than that of the

load. Second question, can I use 220 volt

supply with the device rated 110 volts? Absolutely not! The most crucial

specification in electronics is the voltage level. 3. Can I use a 10A supply to my device rated 50A?

Yes! but the device might not work at 100%. This is the concept behind slow

chargers and fast chargers, the higher the ampere rating and the faster you can

charge. More about this in details when we talk about the types of connection.

That’s it! On our next video we will learn the different types of connection

and how it affects power, voltage and current. If you like the video please

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