3) State and explain in short different eye defect in human beings
4) Explain formation of rainbow with diagram.
5) Explain working and construction of electric motor
6) State different precautions to be taken while handling electric devices
7) Explain importance of earthing in electric circuit
8) Explain different reaction when metal reacts with acid?
9) Explain different reaction of metal with carbonate.
10) What do you mean by hydrides and alkaline and base?
11) What is electrolysis and electrolyte solutions? Give example.
Answers
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3)The defects of vision are also known as defects of eye. (3) Presbyopia. These are the refractive defects of vision because they are caused by the incorrect refraction of light rays by the eye-lens. These defects of vision can be corrected by using suitable spherical lenses (convex lenses or concave lenses).
4)A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun
5)An electric motor is a device which converts electrical energy into mechanical energy. Electric motors and their functions: A power supply – In general, a simple motor has a DC power source. It provides power for the armature of the motor or field coils.
6)1. Avoid water at all times when working with electricity. Never touch or try repairing any electrical equipment or circuits with wet hands. It increases the conductivity of the electric current.
7)2. Never use equipment with frayed cords, damaged insulation or broken plugs.
3. If you are working on any receptacle at your home then always turn off the mains. It is also a good idea to put up a sign on the service panel so that nobody turns the main switch ON by accident.
4. Always use insulated tools while working.
5. Electrical hazards include exposed energized parts and unguarded electrical equipment which may become energized unexpectedly. Such equipment always carries warning signs like “Shock Risk”. Always be observant of such signs and follow the safety rules established by the electrical code followed by the country you’re in.
6. Always use appropriate insulated rubber gloves and goggles while working on any branch circuit or any other electrical circuit.
7. Never try repairing energized equipment. Always check that it is de-energized first by using a tester. When an electric tester touches a live or hot wire, the bulb inside the tester lights up showing that an electrical current is flowing through the respective wire. Check all the wires, the outer metallic covering of the service panel and any other hanging wires with an electrical tester before proceeding with your work.
8. Never use an aluminum or steel ladder if you are working on any receptacle at height in your home. An electrical surge will ground you and the whole electric current will pass through your body. Use a bamboo, wooden or a fiberglass ladder instead.
9. Know the wire code of your country.
10. Always check all your GFCI’s once a month. A GFCI (Ground Fault Circuit Interrupter) is a RCD (Residual Current Device). They have become very common in modern homes, especially damp areas like the bathroom and kitchen, as they help avoid electrical shock hazards. It is designed to disconnect quickly enough to avoid any injury caused by over current or short circuit faults.
8)When an acid reacts with metal, a salt and hydrogen are produced: acid + metal → salt + hydrogen An example: nitric acid + calcium → calcium nitrate + hydrogen The salt that is produced depends upon which acid and which metal react.
9)When acids react with carbonates, such as calcium carbonate (found in chalk, limestone and marble), a salt, water and carbon dioxide are made. ... Also, the reaction of metal carbonates with acids is exothermic (ie heat energy is given out).
10)The compounds formed between the elements and hydrogen are called binary hydrides. ... In fact, on the left side of the periodic table the hydrides of extremely electropositive alkali and alkaline earth metals are not acidic but basic. They are perhaps best considered to be ionic salts of the hydride ion (H−).
11)Electrolytic solutions are those that are capable of conducting an electric current. ... A common example of an electrolyte is ordinary salt, sodium chloride. Solid NaCl and pure water are both non-conductive, but a solution of salt in water is readily conductive.
