Ballpoint pens have a tiny ball made of brass, steel or tungsten carbide as their writing tip. The ball is fitted into a socket and is connected to the ink reservoir by a thin tube. When we write on paper, the ball rolls due to friction between the ball and the paper. This rotating movement allows the thick ink to flow out slowly leaving a mark on the paper.
When drawn over a smooth surface such as glass or plastic there is little friction between the ball and the surface. The ball is unable to rotate and, as a result, the ink cannot flow out. Hence we cannot write on smooth surfaces with a ballpoint pen.
A petrol engine can’t be run with diesel or a diesel engine run with petrol because the engines and their fuels are made for each other. In a petrol engine, for instance, a spark ignites a mixture of petrol vapours and air. This is possible because petrol is highly volatile and easily vaporuizes. Diesel cannot take the place of petrol here because it is less volatile. A different strategy is used in diesel engines. Here, the air is made hot by first compressing it. Diesel is then squirted into the hot air and it burns. Besides, the compression ratio, the difference between the pressure of the fully compressed fuel mixture and atmospheric pressure is much higher in a diesel engine. That is why; diesel cannot be used in place f petrol or vice versa.
When an empty metal vessel is struck, the entire surface of the vessel is set into vibration. The air in contact with the vessel is also set into vibration producing sound of high intensity. If the vessel is partly filled, the surface area of the vessel remaining free to vibrate becomes greatly reduced. Since the total area of air that is set into vibration by the vibrating surface of the vessel also becomes much smaller than in an empty vessel, the intensity of sound also gets reduced.
The earthing of electrical appliances is done as a safety measure. Most of the non-current-carrying metallic parts of an electrical appliance are well insulated and safe to use, but in a faulty appliance current can pass through even these insulated parts and pose a risk to the life of the user. This is because the human body allows an easy flow of electricity through itself to ground. The earthing of the appliances prevents this risk as the earth wire offers a still easier path compared to the human body to the flow of leaking current to ground, thus making the appliance safe to use.
It is easier to balance a long pole on the palm than a short stick because of the higher position of the centre of gravity in the former which normally lies near the middle. For balancing a long pole by holding it upright on its end on our palm what we try to do is to keep its centre of gravity right above the base. As long as the centre of gravity remains straight above the base, the stick remains balanced. But being unstable, it tends to fall and the centre of gravity moves away from the vertical. With a long pole we get sufficient time to move our hand to bring its base directly below its centre of gravity thus restoring balance. But with a short stick we hardly get any time to move our palm to restore the balance and the stick falls down.
A kite flies better without wobbling, spinning or diving if it can keep itself inclined at a specific angle against the blowing wind. This creates a difference in the air-pressure around the kite in such a way that the kite is lifted up. The tail helps a kite in keeping its angle of inclination stable by pulling down its lower tip. Without the tail, wind blowing against the kite and the lift-force generated in turn would send a conventional kite into a tail-spin. Box-kites, however, do not need a tail to stabilize as they do not need to maintain a constant facing angle against the wind to generate the lift. The air swirling through and about a box-kite creates all the pressure differences required to lift up.
stored in microscopic tracks that are made up of ‘pits’ which are grooves and ‘lands’, which are flat surfaces, backed by the shiny, reflective When the player spins the disc, a laser beam shines on these pits and lands. The reflected light patterns are then read by an optical device. This device converts the patterns into little bits of data called, appropriately enough, bits. The bits are assembled into bytes that can in turn represent just about any kind of data imaginable, which includes text, sounds and A DVD has smaller pits than a CD in different vertical layers. A DVD has a much larger data capacity. A standard DVD holds about seven times more data than a CD DVD picture quality is better than that on a CD, and many DVDs have Dolby Digital or DTS sound, which is much closer to the sound you experience in a movie theatre.
First of all, a normal credit card is a simple piece of plastic, but the inside of a smart card usually contains what is called a microprocessor. A microprocessor is the heart of any normal computer, and has the ability to store and update information. Smart cards have many uses in credit cards, ATMs, banking, identification, mobile phones, etc, to name just a few. The microprocessor in the smart card is there for security, and this is one of the greatest advantages of using smart cards
person to discuss matters, they can use video conferencing to share ideas even if they live in different continents. Video conference is a system where computer networks, telephones and video cameras are used to let people see and talk to each E-mail is also an important tool of communication if you have a computer and an internet connection. E-mail is nothing more than sending and receiving messages through your computer. People use e-mail for business, to keep in touch with friends and relatives, and to work on a project with someone a hundred kilometres away. The internet is also used for communicating in chat rooms and newsgroups. You can chat with a friend who is far away by typing or even speaking to him as you would do with a New ways of using computers for communication are being developed at a fast pace. In addition to using videophones to speak to, and see people for way, cars can now find routes to avoid traffic jams, and even give you directions to reach a particular place. ships and trains, planes and spaceships, all depend on computers in one way or the other