Screen

Touch screen working | How Touch Screen Works | Working of smart phone | How touch works in smart phone | Gorilla Touch working | capacitative touch 

An image which showing how touch screen sense touch

An effort of human mind . But this is all happening with technology. We land in an era where everything that can be possibly thought, can also be practically put into . And that too quite reasonably..!! Just move the hand or walk your fingers over a thing and it works. Now you are at Electro Physics . You will get complete knowledge about this technology.

What is touch screen

It is a type of electronic visual display screen which sense pressure . This type of screen designed such that it can sense the zone of pressure and to perform specific task. Now a days these screens are deployed everywhere for better user interface. Screens can be LCD and LED.

There are three types of touch screens we are going to discuss.

1. Resistive Touch :- Resistive touch screen consist mainly two layers one is top flexible layer of Polyethylene and a fixed bottom layer of glass .These layers are coated with a conducting compound-  Indium Tin Oxide.When the monitor is operational, current flows between the two layers. When a user touch the screen, the flexible screen presses down and touches the bottom layer. That leads to a change in current, which detected and the coordinates where touch is made calculated by the controllrer and parsed into readable signals for the operating system to react accordingly. 

Internal View of resistive touch screen

2. Capacitative touch :-  Capacitative touch also called Gorilla touch are different from the resistive touch and Unlike resistive touch screens, a capacitive screens do not work on pressure of your finger to change the flowing current. Instead, they work on the charge ,as a human body comprised of lot of charges (negative and positive) .A Capacitive touch screen is constructed from materials like copper or indium tin oxide because these materials are capable to store electrical charges in an grid of fine and tiny wires, and each of them is smaller than a human hair.

There are two types of capacitive touch screens – one is surface and other is projective. 

1. Surface capacitive screen uses sensors at the corners and a thin uniformly distributed film across the surface (as shown above) 

2. Projective capacitive uses a grid of rows and columns with a dedicated chip for sensing the touch area. In both instances, When a human finger touch the touch screen a small charge exchange between the body and the screen results in completion of circuit , you will amazed if you take a metal glass in your hand and touch the screen your  screen will respond , creating a voltage drop on that point of the screen and that voltage drop sense by the controllers to find out the touch area. That why if a user who wear gloves in his hand not able to perform action on the touch screen. If you want you can touch your screen with current carrying wire you will amazed that it will work.

                                

              As shown in the figure grids as X and Y coordinates 

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Metal inside microwave oven

sparks due to metal foil in the microwave oven | what happened when metal inside microwave oven | Effect on metal due to microwave | fire inside oven due to metal | harmful effect of metal inside oven | can i put metal in the microwave

Fire inside microwave

How Microwave works

Popular microwave generator MAGNETRON . Initially that technology designed for defence. After that a revolutionary use of microwaves which results :- Microwave Oven which use microwaves to cook or heat your food. These are electromagnetic waves ,  in case of microwave oven frequency used is 2.5 gigahertz . At this frequency water ,sugar and fats absorb this waves ( waves are nothing but actually the energy distribution in space ). The absorb energy results into atomic motion which increase the temperature of the stuff . But other material like glass, plastic and ceramic do not absorb them.

Microwave generation

A simple diagram showing generation of the microwave

MAGNETRON ( from wikipedia )

Have you ever wondered why their is metal walls inside the oven?

Because thick piece of metal in wall plays a major role in reflecting the microwave .This is because is there is no metal walls then microwave will spread beyond the microwave boundaries which increase the risk of exposure to radiation. If you were to put your food in a thick metal container in the microwave, it wouldn't cook. Here shielding effect works, due to this effect microwave not able to penetrate into the food instead reflect back. But in other case food in thin metal container would prevent your delicious food from overcooking.

Metal walls inside oven

Microwave source at the top and metal walls

Precaution

Do not use foil container inside microwave

I hope you definitely observe this precaution if you have a microwave in your home. So why microwave manufacturers always write this precaution on their appliance. Reason is the generation of sparks. If you never seen this kind of situation so still you have to read it for future protection. Sometimes the microwave's field mixed up which results in spark ( also called electrical discharge). this mixing is because some items like carrots ( if grown in huge mineral contained soil) etc ( to know more how leave your comment). But major cause is curved or pointed aluminium foil. The major problem arises when the the foil is small, thin and pointed because that foil cannot withstand the flow of microwaves over them and heat until foil ignite. Any thin , or folded ( crinkled)  edges allow current to flow along them which generate a huge potential difference between pointed edge and the microwave walls it's reason is scientific... let me explain:- 

when a charge is supplied on a metal piece which is pointed so here surface charge density works ( surface charge density= charge / surface area ) as area of pointed surface is less so this surface charge density is more which results in generation of huge potential at the sharp point ( this process aso called corona discharge). That potential ionize the air and making path from it's point to wall conducting which generate sparks, setting fire to your food.  

If caught immediately, you can avoid seriously damaging your microwave by simply removing the offending bit of metal. However prolonged microwaving of metal (or wadding up an entire roll ) will likely cause irreparable harm to the appliance and probably set other parts your kitchen on fire.

That would be the result if you do not follow the instruction.

Be safe.................