 Hi, my name is Prabhakar, I am with IIT Kanpur. In this lecture, let us look at phones, smartphones, phablets and tablets. So we know that there are phones and there are smartphones. So what is the difference between a phone and a smartphone? A smartphone typically is an advanced computing device. It has what we call apps, apps is an acronym for applications. It can run small programs. The user can program, anybody in the world can program which are loaded into the smartphone and they can be executed. Of course it also has advanced computing and connectivity features. By this we mean it has Wi-Fi and so on. And what is a phablet? A phablet is nothing but a phone with a large screen. It is actually in between a phone and a tablet whereas a tablet may not be able to make a phone call, a phablet typically has the ability to make a phone call. So if you look at the progression of these devices, the smallest is the phone in size. The next is the smartphone and then we have a phablet and then we have a tablet. So what is the typical size of a phone or a smartphone to a tablet? So the sizes look like this. The size of device is measured by the diagonal of the screen. So it's normally measured in inches and if you take a phone or a smartphone it is in the range of 3 to 5 inches and a phablet is bigger in the range of 5 to 7 inches and tablets are in the range of 7 to 11 inches. Another parameter of a phone is how much does it weigh? So smartphones and phablets are in the region of 100 to 170 grams. Normally we are carrying them on our body in our pockets or purses and we don't want them to be very heavy and tablets because they are bigger, they are in the range of 500 to 700 grams, half a kilo. In terms of connectivity, these phones allow us to connect using cellular networks. We know about 3G, 2G kind of networks, we are going to study more of these in the rest of the course and then there is connectivity using Wi-Fi or Bluetooth. Many of them have speakers, loud speakers that in the sense you can get the volume loud. Some of you want to hear it together, you can keep the speaker on or sometimes when the voice is not coming out clearly having the loud speaker on is helpful. It has a microphone into which you talk to and then there are cameras, some of these smartphone cameras are actually very good and very powerful. They are even actually replacing point and click cameras. It has capacitive multi-touch screens and then you can connect through a what is called a USB port, it's a micro USB port. This is normally how it looks, this is the standard USB and this is the micro USB. Now what are capacitive multi-touch screens? These are screens with which you interact with the phone. You can give input to the screen to the phone. Capacitive as against resistive touch. Some phones earlier generation touch devices used to be resistive touch but they are no longer in vogue. So these capacitive devices actually rely on the electrical property of the human skin, the body to detect a touch. So that's why they are very sensitive and of course then you cannot use it with gloves and if you want to ride you need a special pen. If you are using a capacitive touch screen phone and you want to use a stylus then you need a different kind of pen to write with. These phones are supposed to be oleophobic. What is oleophobic screen? It basically means it doesn't smudge, the oil is repelling. Suppose for example I have the phone here with fingerprints on it, I just need to wipe it off and it will go away. So oleum is Latin, in Latin is oil and phobos is fierce, oil doesn't stick, oil is repelled. The screen is made of what is called Gorilla Glass which is very powerful and strong glass thin and strong and that's what is used in most of the phones. You can connect keyboards or mouse to interact with the phone and this connectivity is normally through Bluetooth connection. Now the battery is a very, very important parameter of the phone, normally it gives about 5 to 10 hours of working time. So the capacity of a battery is measured in what is called milli ampere hours and this number is in the range of 2000 to 10,000 milli ampere hours based on the size of the phone and whether it's a tablet or a tablet and so on. Obviously, a larger size means the phone will last longer before the second charge. Now a phone is consuming energy, right? It's you charge it every day or once into three days. So how much does it consume? Is it like an electric lamp or like a refrigerator or how much is it? So typically a smartphone is in the range of 2 to 4 kilowatt hours per year. A kilowatt hour is one unit, right? That means if you take a 100 watt lamp and run it for 10 hours, you will consume 1 unit. So that is the amount of energy that a smartphone consumes in one full year. Of course, a laptop for comparison consumes a lot more energy. It's about 20 times the consumption of a smartphone and of course, this is assuming that you charge it fully one every day. So whatever the capacity of the phone is, you charge it in the morning and let's say by you discharge it by evening fully, that means you have consumed all the energy in the battery, okay? That's when you get these kinds of estimates. It's about 3 to 4 units of energy per year. So homework for you, what is the capacity of your phone battery? Find out, thank you.