In case of motor car battery or automotive batteries a nominal 12-volt potential difference is provided by connecting six galvanic cells in series. Capacity of these batteries is expressed in amperehour. Electrolyte used is a solution of about 35% sulphuric acid and 65% water and electrodes used are plates of lead and separate plates of lead dioxide.

A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapour. The excited mercury atoms produce shortwave ultraviolet light that then causes a phosphor to fluoresce, producing visible light .In fluorescent tubes the simplest ballast for alternating current use is an inductor (choke coil) placed in series, consisting of a winding on a laminated magnetic core. The inductance of this winding limits the flow of AC current on account of its large impedance. The only waste of energy is due to the hysteresis loss in the iron core, which is much less than the waste of energy in comparison to resistance which can also reduce the current if placed instead of the choking coil.

Resistance (R) of a length l, resistivity p and area of cross-section A is given by
For the two wires,

An alternating current (a.c.) is one which is constantly changing direction. Alternating current have two cycles positive half cycle and negative half cycle. Mains electricity is an a.c. supply which is supplied to homes in India at 220 V AC at 50 Hz. Thus, in our houses the current in A.C. electricity line changes direction = 50 * 2 = 100 times per second.

Human body has different resistance when human body dry then the resistance is 10⁵ ohms, and when human body wet because of water or sweet then the resistance is 1000 ohms, so for dry skin the resistance is 10⁴ ohms. Hence option (b) is correct.

A fluorescent lamp or fluorescent tube is a gasdischarge lamp that uses electricity to excite mercury vapour. The excited mercury atoms produce shortwave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. 6500 K is usually printed on a used fluorescent tubelight.

Earth’s magnetic field diverts them torwards its poles.

Gravity is the feeble force among the four.

Frequency modulation : It is a process in which the frequency of the carrier is varied in accordance with the instantaneous value of modulating voltage. In telecommunications and signal processing, frequency modulation (FM) conveys information over a carrier wave by varying its instantaneous frequency. FM is most commonly used for radio and television broadcasting.

Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. At present solar energy in our country is used for solar water heater. Solar lights that charge during the day and light up at night are a common sight along walkways.

An astronomical unit (abbreviated as AU, au or a.u.) is a unit of length equal to about 149,597,870.7 kilometers or approximately the mean Earth-Sun distance. The astronomical constant whose value is one astronomical unit is referred to as unit distance and is given by the symbol A.

In compact disc digital data is scanned by laser beam for the reproduction of recorded sound.

Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Like all other electromagnetic waves, they travel at the speed of light. Artificially-generated radio waves are used for fixed and mobile radio communication, broadcasting, radar and other navigation systems, satellite communication, computer networks and innumerable other applications.

A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. The most common use of nuclear reactors is for the generation of electrical power and for the power in some ships. In every fission reaction in which uranium nuclei splits up to give smaller nuclei three more neutrons are produced which further results into splitting of heavy uranium nuclei and more number of neutrons will be produced. Thus, statement, 1 and 2 are correct. In nuclear reactor all the neutrons produced can not take part in fission reaction, else reaction can turn out extremely violent. Thus, graphite rods are used as a control rods to slow down the speed of fast moving neutrons. Thus, statement 3 is also correct.

The geostationary satellite is a satellite having a time-period of 24 hours. Using this time-period, the height of the satellite comes out to be approximately 35,800 km. FM broadcasting is a broadcast technology pioneered by Edwin Howard Armstrong that uses frequency modulation (FM) to provide high-fidelity sound over broadcast radio. FM transmission is quite immune to noise as compared to AM transmission. Noise is a form of amplitude variations in the transmitted signal due to atmosphere, industries, etc.

Dolby B and C are the noise reduction circuits developed by Dolby laboratories. Dolby noise reduction has made it possible to protect the music from tape noise, and helped make cassette the most popular audio product ever devised.

X-ray computed tomography (CT) is a medical imaging method employing tomography created by computer processing. This technique is used to generate a three-dimensional image of the inside of an object.

When pure hydrogen is used as the fuel, the only by-products generated from the fuel cell are pure water and heat. Similar to a battery, a fuel cell with a supply of hydrogen and oxygen can be used to power devices that use electricity.

A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel or oxidiser, that is, its fuel or oxidizer (or both) are gases liquefied and stored at very low temperatures. Notably, these engines were one of the main factors of the ultimate success in reaching the Moon by the Saturn V rocket. Various cryogenic fuel-oxidizer combinations have been tried, but the combination of liquid hydrogen fuel and the liquid oxygen oxidizer is one of the most widely used.

There is a presence of atmosphere at earth’s surface which consists of thick and moving layers of air. The dust particles, particulates, smog, water vapour and smoke are also present in air. Stars twinkle when we see them from the Earth’s surface because we are viewing them through thick layers of turbulent (moving) air in the Earth’s atmosphere. As their light travels through the many layers of the Earth’s atmosphere, the light of the star is bent (refracted) many times in random directions (light is bent when it hits a change in density –like a pocket of cold air or hot air). This random refraction results in the star as its twinkling but for a person in spaceship no such refractions are possible as there is vaccum in space. Thus, star will not twinkle.
Similarly, sky will appear blue to us due to Rayleigh scattering which is again due to presence of atmosphere on earth’s surface. The shorter wavelength light is absorbed by the gas molecules of atmosphere. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Some of this scattered blue light reaches you. Since, you see, the sky looks blue. Whereas no atmosphere is there in space thus, no absorbing and scattering is possible that’s why for a person in spaceship sky appears black. Temperature outside the spaceship is higher in comparison to earth’s surface because of being nearer to sun.