General Science Previous Year Questions (PYQ) with Answers – Page 41

Teflon is the trade name of polytetrafluoroethylene, a polymer whose surface is one of the most slippery among solids, with a coefficient of friction of about 0.04.

Water has a specific heat capacity of about 4186 joule per kilogram per kelvin, not 1200, so this pair is the wrong one.

The force on a current-carrying conductor placed in a magnetic field is found with Fleming's left-hand rule.

Electrical energy is power multiplied by time, so the unit follows directly from the units you put in. The oven is rated 2500 W, which is 2500 divided by 1000, that is 2.5 kilowatts.

Germanium is not used to build light emitting diodes because it is an indirect band gap semiconductor, so an electron falling back across the gap gives up most of its energy as heat in the crystal rather than as light.

All three are unicellular, which means a single cell carries out every job of life. In a unicellular organism that one cell manages nutrition, respiration, movement and reproduction, while a multicellular body shares the work among tissues and organs.

Acoustics is the branch of physics that deals with how sound is produced, how it travels and how it is heard or absorbed.

Drosera, known as the sundew, is an insect-eating plant whose leaves are covered with stalked glands tipped with a shining drop of sticky fluid.

The force on a current carrying conductor kept in a magnetic field is given by F equal to B I L sin theta, where theta is the angle between the direction of the current and the direction of the field.

In 1820 the Danish scientist Hans Christian Oersted saw that a compass needle kept near a wire swung aside the moment a current flowed through the wire, and swung the other way when the current was reversed.

Soil acidity is measured on the pH scale, and pH depends on the concentration of hydrogen ions in the soil water.

The carbohydrates in our food are broken down into glucose, and the glucose that the body does not need at once is stored as glycogen, a branched chain of glucose units kept mainly in the liver and the skeletal muscles.

An alkyne contains a carbon to carbon triple bond, which needs at least two carbon atoms, so the series begins with ethyne, C2H2, also called acetylene and used with oxygen in welding.

The prefix di stands for two and the ending ene for a carbon to carbon double bond, so a diene is a hydrocarbon carrying exactly two such bonds; buta-1,3-diene, the raw material of synthetic rubber, is the standard example.

Bryophytes live on land but still need water to complete reproduction, so they are called the amphibians of the plant kingdom.

Brass takes the workability of copper and the hardness of zinc, resists corrosion and is easy to cast, which is why it is used for utensils, locks, taps, fittings and wind instruments.

Ductility is the property of being drawn into a wire, and gold is the most ductile metal known; it is also the most malleable, so a very small quantity can be beaten into an extremely thin sheet or drawn into a very long wire.

Carotenoids are the yellow, orange and red pigments inside the chloroplast that absorb sunlight and hand the energy on to chlorophyll, so they are the only choice here that traps light for photosynthesis.

Blood is filtered in the glomerulus of the nephron, and the filtrate that first enters the tubule still holds many useful substances.

Gases move across the cell membrane by diffusion, the spread of particles from a region where they are more concentrated to a region where they are less concentrated.