REFLECTION

Q1:  Explain why a ray of light passing through the centre of curvature of a concave mirror gets reflected along the same path.

Q2:  What is the nature of image formed by a concave mirror if the magnification produced by the mirror is +3?

Q3:  Write two different uses of concave mirrors.

Q4:  An object is kept at a distance of 4m in front of a special mirror which forms its erect image at a distance of 1.0 m from the mirror. What is the magnification? Is the mirror concave or convex?

Q5:  A ray of light LM is incident on a mirror as shown in the figure. The angle of incidence for this ray is the angle between it and the line joining two other points in the figure. Name these two points.

REFRACTION

Q6:  Why does a ray of light bend when it travels from one medium into another?

Q7:  Name the component of white light that has the greatest wavelength.

Q8:  How should a ray of light be incident on a rectangular glass slab so that it comes out from the opposite side of the slab without being displaced?

Q9:  The following table gives the values of refractive indices of few media.

 S.No. 1 2 3 4 5 Medium Water Crown Glass Rock Salt Ruby Diamond Refractive Index 1.33 1.52 1.54 1.71 2.42

Use this table to give an example of a medium pair so that light speeds up when it goes from one of these media to another.

Q10:  Draw the given diagram in your answer book and complete it for the path of ray of light beyond the lens.

Q11:  A girl was playing with a thin beam of light from her laser torch by direction it from different directions on a convex lens held vertically.  She was surprised to see that in a particular direction the beam of light continues to move along the same direction through the lens.  State the reason for this observation.

Q12:  Define power of a lens.

HUMAN EYE

Q13:  Name the part of our eyes that helps us to focus near and distant objects in quick succession.

NATURAL PHENOMENA

Q14:  Why does sky look blue on a clear day?

Q15:  List the three phenomena of light responsible for formation of rainbow in the sky?

Q16:  Why do we see stars twinkling whereas, planets do not twinkle?

ELECTRICITY

Q17:  Generally, alloys are used in electrical heating devices instead of pure metals. What could be the reason?

MAGNETISM

Q18:  A charged particle enters at right angles into a uniform magnetic field as shown.  What should be the nature of charge on the particle if it begins to move in a direction pointing vertically out of the page due to its interaction with the magnetic field?

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PHYSICS

FIRST – There will be a total of 26 QUESTIONS in the Physics Paper of 70 Marks

SECOND – All the 26 Questions are compulsory.

THIRD The Physics Question Paper is divided into five Sections. Section A, Section B, Section C, Section D and Section E.

FOURTH

Section A: 5 Questions each of 1 – mark totalling 5 marks

Section B: 5 Questions each of 2 – mark totalling 10 marks

(Choice available in one Question)

Section C: 12 Questions each of 3 – mark totalling 36 marks

(Choice available in one Question)

Section D: 1 Value Added Question of 4 – mark totalling 4 marks

Section E: 3 Questions each of 4 – mark totalling 15 marks

(in all 3 Questions have Choice)

Many metals form ionic bonds when they react with non-metals. Compounds so formed are known as ionic compounds.

Ions: Positive or negative charged atoms are known as ions. Ions are formed because of loss or gain of electrons. Atoms form ion to obtain the electronic configuration of nearest noble gas, this means to obtain stable configuration.

### Check out the complete list of TOPICS in the ‘LIST’

CLASS X CHEMISTRY – 25 Marks

Chemical Reactions: Chemical equation, Balanced chemical equation, implication of a balanced chemical equation, types of chemical reactions: Combination, decomposition, displacement, double displacement, precipitation, neutralization, oxidation and reduction.

Acids, Bases and Salts : Their definitions in terms of furnishing of H+ and OH- ions, General properties, examples and uses, concept of pH scale (Definition relating to logarithm not required), importance of pH in everyday life; preparation and uses of Sodium Hydroxide, Bleaching powder, Baking soda, Washing soda and Plaster of Paris.

Metals and Non-Metals: Properties of metals and non-metals; Reactivity series; Formation and properties of ionic compounds; Basic metallurgical processes; Corrosion and its prevention.

Carbon Compounds: Covalent bonding in carbon compounds. Versatile nature of carbon. Homologous series. Nomenclature of carbon compounds containing functional groups (Halogens, Alcohol, Ketones, Aldehydes, Alkanes and Alkynes), difference between saturated hydrocarbons and unsaturated hydrocarbons. Chemical properties of carbon compounds (combustion, oxidation, addition and substitution reaction). Ethanol and Ethanoic acid (only properties and uses), soaps and detergents.

Periodic Classification of Elements: Need for classification, Early attempts at classification of elements (Dobereiner’s Triads, Newland’s Law of Octaves, Mendeleev’s Periodic Table), Modern periodic table, gradation in properties, valency, atomic number, metallic and non-metallic properties.

CLASS X PHYSICS

Natural Phenomena —12 Marks

Light: Reflection of light by curved surfaces; Images formed by spherical mirrors, centre of curvature, principal axis, principal focus, focal length, mirror formula (Derivation not required), magnification.

Refraction; Laws of refraction, refractive index.

Refraction of light by spherical lens; Image formed by spherical lenses; Lens formula (Derivation not required); Magnification. Power of a lens. Functioning of a lens in human eye, defects of vision and their corrections, applications of spherical mirrors and lenses. Refraction of light through a prism, dispersion of light, scattering of light, applications in daily life.

Effects of Current —-13 Marks

Electric current, potential difference and electric current. Ohm’s law; Resistance, resistivity, Factors on which the resistance of a conductor depends. Series combination of resistors, parallel combination of resistors and its applications in daily life. Heating effect of electric current and its applications in daily life. Electric power, Interrelation between P, V, I and R.

Magnetic Effects of Current : Magnetic field, field lines, field due to a current carrying conductor, field due to current carrying coil or solenoid; Force on current carrying conductor, Fleming’s Left Hand Rule, Electric Motor, Electromagnetic induction. Induced potential difference, Induced current. Fleming’s Right Hand Rule, Electric Generator, Direct Current. Alternating Current

CLASS X BIOLOGY– 23 Marks

Life Processes: ‘Living Being’. Basic concept of nutrition, respiration, transport and excretion in plants and animals.

Control and Co-Ordination in Animals and Plants: Tropic movements in plants; Introduction of plant hormones; Control and co-ordination in animals; Nervous system; Voluntary, involuntary and reflex action; Chemical co-ordination: animal hormones.

Reproduction: Reproduction in animals and plants (asexual and sexual) reproductive health-need and methods of family planning. Safe sex vs HIV / AIDS. Childbearing and women’s health.

Heredity and Evolution: Heredity; Mendel’s contribution – Laws for inheritance of traits: Sex determination: brief introduction; Basic concepts of evolution.

Natural Resources – 07 Marks

Sources of Energy: Different forms of energy, conventional and non-conventional sources of energy: Fossil fuels, solar energy; biogas; wind, water and tidal energy; Nuclear energy. Renewable versus non-renewable sources of Energy.

Our Environment : Eco-system, Environmental problems, Ozone depletion, waste production and their solutions. Biodegradable and non-biodegradable substances.

Management of Natural Resources : Conservation and judicious use of natural resources. Forest and wild life; Coal and Petroleum conservation. Examples of people’s participation for conservation of natural resources. Big dams: advantages and limitations; alternatives, if any. Water harvesting. Sustainability of natural resources.

## Marking Scheme for Class X Science Paper for 2018

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Domestic Circuit

1. Most power stations constructed these days produce AC current. In India, the AC changes direction after every 1/100 second, that is, the frequency of AC is 50 Hz.

2. In our homes, we receive a supply of electric power from the main supply (also called mains), either supported by overhead electric poles or by underground cables.

3. One of the wires in this supply, usually with red insulation cover, is called live wire (or positive). Another wire, with black insulation, is called neutral wire (or negative). In our country, the potential difference between the two is 220 V.

4. At the meter-board in the house, these wires pass into an electricity meter through the main fuse.

5. Through the main switch, they are connected to the line wires in the house. These wires supply electricity to separate circuits within the house.

6. Often, two separate circuits are used, one of 15A current rating for appliances with higher power ratings such as geysers, air coolers, etc. The other circuit is of 5A current rating for bulbs, fans, etc.

7. The earth wire, which has the insulation of green colour, is usually connected to a metal plate deep in the earth near the house. This is used as a safety measure, especially for those appliances that have a metallic body, for example, electric press, toaster, table fan, refrigerator, etc. The metallic body is connected to the earth wire, which provides a low-resistance conducting path for the current. It ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, and the user may not get a severe electric shock.

8. The figure below gives a schematic diagram of one of the common domestic circuits. In each separate circuit, different appliances can be connected to the live and neutral wires. Each appliance has a separate switch to ‘ON’/‘OFF’ the flow of current through it. In order that each appliance has an equal potential difference, they are connected parallel to each other.

9. An electric fuse is an important component of all domestic circuits. A fuse is a device used for preventing damage to the appliances and the circuit due to overloading.

10. Overloading can occur when the live wire and the neutral wire come into direct contact. (This occurs when the insulation of wires is damaged or there is a fault in the appliance.) In such a situation, the current in the circuit abruptly increases. This is called short-circuiting. The use of an electric fuse prevents the electric circuit and the appliance from a possible damage by stopping the flow of unduly high electric current. The Joule heating that takes place in the fuse melts it to break the electric circuit. Overloading can also occur due to an accidental hike in the supply voltage. Sometimes overloading is caused by connecting too many appliances to a single socket.

### Check out the complete list of TOPICS in the ‘LIST’

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Electric Generator

1. An electric generator is a device where mechanical energy is used to rotate a conductor in a magnetic field to produce electricity.

2. An electric generator consists of a rotating rectangular coil ABCD placed between the two poles of a permanent magnet. The two ends of this coil are connected to the two rings R1 and R2. The two conducting stationary brushes B1 and B2 are kept pressed separately on the rings R1 and R2, respectively. The two rings R1 and R2 are internally attached to an axle.

3. The axle is mechanically rotated from outside to rotate the coil inside the magnetic field. Outer ends of the two brushes are connected to the galvanometer to show the flow of current in the given external circuit.

4. When the axle is rotated such that the arm CD moves up (and the arm AB moves down) in the magnetic field produced by the permanent magnet. Coil ABCD is rotated anticlockwise in the arrangement. By applying Fleming’s right-hand rule, the induced currents are set up in these arms along the directions AB and CD. The induced current flows in the direction DCBA.

5. If there are larger numbers of turns in the coil, the current generated in each turn adds up to give a large current through the coil. This means that the current in the external circuit flows from B1 to B2. After half a rotation, arm AB starts moving up and CD moving down. As a result, the directions of the induced currents in both the arms change, giving rise to the net induced current in the direction ABCD. The current in the external circuit now flows from B2 to B1.

6. After every half rotation, the polarity of the current in the respective arms changes. Such a current, which changes direction after equal intervals of time, is called an alternating current (abbreviated as AC). This device is called an AC generator.

7. To get a direct current (DC, which does not change its direction with time), a split-ring type commutator must be used. With this arrangement, one brush is used at all times in contact with the arm moving up in the field, while the other is in contact with the arm moving down. Thus, a unidirectional current is produced. The generator is thus called a DC generator.

Difference between DC and AC

8. The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically.

9. An important advantage of AC over DC is that electric power can be transmitted over long distances without much loss of energy.

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