General Science Previous Year Questions (PYQ) with Answers – Page 94

The standard hydrogen electrode has a real, non-zero potential; it is only assigned the value zero by convention. The absolute potential of a single electrode cannot be measured, because any measurement needs a second electrode to complete the circuit.

Hydrogen shows 0, +1 or -1 depending on what it is bonded to. In the free element H2 its oxidation number is 0, as for every element in its uncombined state.

As one climbs, air pressure falls, so each breath delivers oxygen at a lower partial pressure and less of it passes from the lungs into the blood.

The 2015 film 'The Man Who Knew Infinity' tells the life of the Indian mathematician Srinivasa Ramanujan and is based on Robert Kanigel's 1991 biography of the same name.

Mature human red blood cells and platelets have no nucleus. Red blood cells lose their nucleus as they mature in the bone marrow; this gives their biconcave disc shape more room for haemoglobin to carry oxygen, but it also means they cannot divide or repair themselves and live only about…

Insulin lets glucose leave the blood and enter body cells, especially muscle and fat cells, and so it lowers the blood sugar level.

The statement that the sensitivity of the human ear does not vary with frequency is false, because the ear is far more sensitive to some frequencies than to others.

Planck's constant has the same dimensions as angular momentum, [M L² T⁻¹].

Standard atmospheric pressure at sea level is defined as the pressure of a 760 mm column of mercury at 0 °C. In 1643 Evangelista Torricelli showed that air pressure holds up a column of mercury about 760 mm (76 cm) tall in a glass tube, inventing the mercury barometer.

The base is made thin and lightly doped so that most charge carriers from the emitter cross it to the collector.

A gamma ray is a photon of energy with no mass and no charge, so emitting it leaves the count of protons and neutrons unchanged.

Lithium hydrogen carbonate exists only in solution; it cannot be isolated as a solid. All the alkali metals of group 1 form hydrogen carbonates (bicarbonates), but lithium behaves differently from the rest.

Too little fluoride weakens tooth enamel and makes teeth prone to decay, known as dental caries. Fluoride becomes part of the enamel as fluorapatite, which resists the acids made by mouth bacteria from sugars.

Dolomite is a carbonate of calcium and magnesium, a base that neutralises soil acidity and so raises the pH. Dolomite, CaMg(CO₃)₂, is a common liming material.

The 2011 FSSAI labelling rules made the list of ingredients, nutrition information and the vegetarian or non-vegetarian mark compulsory, but not medical advice on allergies.

In paper making the raw plant material is cooked with caustic soda, which dissolves the gums, resins and lignin that bind the cellulose fibres together.

Coal is an impure fossil fuel containing hydrogen, oxygen, nitrogen and sulphur besides carbon, so it is not a pure form of the element.

HIV infects and destroys helper T lymphocytes, the white blood cells that coordinate the body's immune response, so immunity steadily collapses.

In such a fluid the shearing stress is directly proportional to the rate of shear, so the coefficient of viscosity, which measures the resistance to deformation, keeps the same value whatever the stress applied; water, air, petrol and thin oils behave in this way.

When the ray makes 90 degrees with the surface it is travelling along the normal, so the angle of incidence measured from the normal is zero and the ray goes straight on without bending.