In filament lamps a good part of the electrical energy is used up in heating the filament which in turn glows throwing light around. While in fluorescent tubes light is produced by electrical discharge in a glass tube, the inside of which is coated with a fluorescent material. The filaments at the two ends are used only to start the discharge. The discharge passing through vapours of mercury produce UV radiations which excites the fluorescent coating producing visible light. Since very little heating is involved in the process and most of the electrical energy is used in producing light, fluorescent tubes consume less power than filament lamps.
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.
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.[custom_search_and_filter]