Science & Tech — Prelims MCQs

India is an important member of the 'International Thermonuclear Experimental Reactor'. If this experiment succeeds, what is the immediate advantage for India?

With reference to the colours we see in the sky, consider the following statements:

1. The sky looks blue because the molecules of air scatter the shorter waves of sunlight, such as blue, much more strongly than the longer ones, such as red.
2. The Sun looks reddish at sunrise and sunset because its light then travels a longer path through the atmosphere, and most of the blue is scattered away before the light reaches the eye.
3. A rainbow is formed when sunlight enters raindrops, is bent and separated into colours, and is reflected inside the drops back towards the observer.
4. The sky would still look blue to an astronaut standing on the Moon, because sunlight is itself blue in colour.

How many of the statements given above are correct?

With reference to the way electricity is carried from a power station to a household, consider the following statements:

1. Electricity is sent over long distances at a very high voltage because, for the same power delivered, a higher voltage means a smaller current, and the heat wasted in the wire depends on the current.
2. A transformer can raise or lower a voltage only when the current passing through it keeps changing, which is one of the main reasons the grid is built on alternating current.
3. While stepping the voltage up, a transformer also increases the electrical power passing through it.
4. The high voltage of a transmission line is brought down in stages, so the supply reaching a household is at a far lower voltage than the line leaving the power station.

How many of the statements given above are correct?

On a cold morning a steel spoon and a wooden spoon have been lying side by side on a table in the same room all night. When they are picked up, the steel spoon feels much colder than the wooden one. Which one of the following best explains this?

With reference to enzymes in the human body, consider the following statements:

1. An enzyme speeds up a chemical reaction by lowering the energy needed to start it, and the enzyme itself is not used up in that reaction.
2. An enzyme acts only on a limited range of substances, because its action depends on a particular part of the enzyme fitting the shape of the substance.
3. Boiling a solution containing an enzyme makes the enzyme work faster, since chemical reactions in general go faster at a higher temperature.
4. Enzymes work equally well at any level of acidity, because only temperature affects how an enzyme behaves.

How many of the statements given above are correct?

Consider the following pairs of materials and the property that makes each one suitable for the use given:

1. Tungsten, used as the glowing filament of an ordinary electric bulb — it melts at a higher temperature than any other metal, so it can be kept white-hot without melting away
2. Copper, used for the wiring in a house — it lets an electric current pass easily and can be drawn out into a long thin wire without breaking
3. Graphite, used as a pencil lead and as a dry lubricant — its carbon atoms are joined into flat sheets that slide over one another easily
4. Diamond, used in cutting and drilling tools — each of its carbon atoms is joined to four others in a rigid three-dimensional network, which makes it extremely hard

How many of the pairs given above are correctly matched?