Odisha BSE HSC General Science flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Mirror formula

The relation 1/v + 1/u = 1/f linking object distance u, image distance v and focal length f of a spherical mirror; the magnification is m = -v/u.

Power of a lens

P = 1/f when focal length f is expressed in metres; the unit is the dioptre (D). A convex lens of focal length 20 cm has power +5 D.

Refractive index of glass

n = c/v, the ratio of the speed of light in vacuum to its speed in the medium. Glass has n about 1.5, so light travels 2 x 10^8 m/s inside it.

Ohm's law

At constant temperature, the current through a metallic conductor is directly proportional to the potential difference across it, so V = IR with R measured in ohms.

Equivalent resistance in parallel

The reciprocal of the total resistance equals the sum of the reciprocals, 1/R = 1/R1 + 1/R2. The result is always smaller than the smallest individual resistance.

Fleming's left-hand rule

With thumb, forefinger and middle finger of the left hand mutually perpendicular, the thumb gives the force on a current-carrying conductor, the forefinger the magnetic field and the middle finger the current.

Myopia

Near-sightedness in which distant objects look blurred because the image forms in front of the retina; it is corrected by a concave, diverging lens of suitable negative power.

Right-hand thumb rule

Holding a straight current-carrying conductor with the right thumb along the current, the curled fingers give the direction of the magnetic field, whose lines are concentric circles around the wire.

One kilowatt-hour

The commercial unit of electrical energy, equal to the energy used by a 1 kW appliance running for one hour; one kWh equals 3.6 x 10^6 joules.

Neutral solution pH

A pH of exactly 7, as in pure water, where hydrogen ion and hydroxide ion concentrations are equal and litmus paper keeps its neutral purple colour.

Neutralisation reaction

A reaction between an acid and a base that produces a salt and water, for example HCl + NaOH gives NaCl + H2O. The reaction generally releases heat.

Reactivity series

The order of metals by chemical reactivity: K, Na, Ca, Mg, Al, Zn, Fe, Pb, Cu, Hg, Ag, Au. A metal higher in the list displaces a lower metal from its salt solution.

Rusting of iron

Corrosion that needs both oxygen and moisture and produces hydrated iron(III) oxide. It is prevented by painting, oiling, galvanising with zinc or alloying to make stainless steel.

Plaster of Paris

Calcium sulphate hemihydrate, CaSO4.1/2H2O, made by heating gypsum to 373 K. Mixed with water it sets hard as CaSO4.2H2O for casts and moulds.

Catenation

The ability of an element to link its own atoms into long chains and rings. Carbon shows this strongly and therefore forms millions of organic compounds.

Ionic bond

Formed when one atom transfers electrons to another, producing a cation and an anion held together by electrostatic attraction, as in sodium chloride; such compounds conduct electricity when molten.

Displacement reaction

A reaction in which a more reactive element pushes a less reactive one out of its compound, such as zinc or iron turning blue copper sulphate solution pale and colourless.

Baking soda

Sodium hydrogen carbonate, NaHCO3, a mild base used in cooking and in antacids; on heating it releases carbon dioxide, which makes cakes and bread rise.

Nephron

The microscopic functional unit of the kidney, about a million in each kidney, which filters blood in the glomerulus and reabsorbs glucose, salts and water from the filtrate.

Reflex arc

The nerve pathway of a fast automatic response: receptor, sensory neuron, relay in the spinal cord, motor neuron and effector muscle or gland.

Insulin

A hormone secreted by the beta cells of the pancreas that lowers blood glucose by helping cells absorb it; its deficiency causes diabetes mellitus.

Stomata

Tiny pores in the leaf epidermis surrounded by guard cells; they let carbon dioxide enter for photosynthesis and allow oxygen and water vapour to escape.

Sex determination in humans

The mother contributes an X chromosome while the father contributes either X or Y; XX offspring are female and XY offspring are male, so the father determines the child's sex.

Monohybrid F2 ratio

In Mendel's pea crosses the second filial generation showed 3 tall to 1 dwarf plant, a 3:1 phenotypic ratio, with genotypes 1 TT : 2 Tt : 1 tt.

Platelets

Small cell fragments in blood that clump at a wound and start clotting by converting fibrinogen into fibrin threads, so that bleeding stops.

Haemoglobin

The iron-containing red pigment of red blood cells that binds oxygen in the lungs and releases it in the tissues; its deficiency causes anaemia.

Ten per cent law

Lindeman's rule that only about ten per cent of the energy at one trophic level passes to the next, the rest being lost mainly as heat during respiration.

Ozone depletion

Thinning of the stratospheric ozone layer by chlorine and bromine released from chlorofluorocarbons and halons, allowing more ultraviolet radiation to reach the Earth's surface.

Non-biodegradable waste

Material such as polythene, plastic, glass or DDT that micro-organisms cannot break down, so it persists in soil and water and accumulates through food chains.

Eutrophication

Enrichment of a water body with nitrates and phosphates from fertilisers and sewage, causing algal blooms whose decay removes dissolved oxygen and kills fish.

Acid rain

Rainfall with pH below about 5.6, formed when sulphur dioxide and nitrogen oxides from burning fossil fuels dissolve in atmospheric moisture and fall as dilute acids.

Chipko movement

A 1973 Himalayan movement in which villagers, especially women, hugged trees to prevent felling, an example of community-led forest conservation in India.