Thursday, March 24, 2016

important question paper science

PRE-BOARD EXAMINATION(II)

Class- X

Subject - Science

Time : 2½ Hours Max. Marks : 60

General Instructions

1. The question paper comprises of two sections A and B. You are to attempt both

the sections.

2. All questions are compulsory.

3. There is no overall choice However, internal choice has been provided in all the

three questions of five marks category. Only one option in such questions is to be

attempted.

4. All questions of section A and all questions of section B are to be attempted

separately.

5. Questions 1 to 6 in section A and 17 to 19 in section B are short question. These

carry one mark each.

6. Questions 7 to 10 in section A and 20 to 24 in section B are short answer type

questions and carry two marks each.

7. Questions 11 to 14 in section A and 25 to 26 in section B are also short answer

type questions and carry three marks each.

8. Questions 15 and 16 in section A and question 27 in section B are long answer

type questions and carry five marks each.

SECTION A

If a mirror has a focal length of -25 cm, what will be its radius of curvature and nature? 1
Write chemical equations for reactions taking place when Manganese dioxide is heated with aluminium powder. 1
During summer season, a milkman usually adds a very small amount of baking soda to fresh milk. Give one reason. 1
What is the angle of reflection if a ray falls normally on a plane mirror? 1
Can a displacement reaction be a redox reaction? Explain with example. 1
An electric geyser has the ratings 2000W, 220V marked on it. What should be the minimum rating, in whole number of a fuse wire, that may be required for safe use with this geyser? 1
A solution of a substance ‘X’ is used for testing CO_2.Identify ‘X’. What will be its reaction with Carbon dioxide? Write balanced chemical equation for the reaction. 2
A student has been collecting silver coins and copper coins. One day she observed a black coating on silver coins and a green coating on copper coins. Which chemical phenomenon is responsible for these coatings? Write the chemical name of black and green coatings. 2
Differentiate between short circuiting and overloading of electrical circuits. How does a fuse protects an electrical circuit? 2
Draw the pattern of magnetic field lines of a current carrying solenoid. What does the pattern of field lines inside the solenoid indicate? Write one application of magnetic field of current carrying solenoid. 2
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet:

(a) pushed into the coil

(b) withdrawn from inside the coil

(c) held stationary inside the coil. 3

Two compounds ‘A’ and ‘B’ have the same molecular formula C4H8O2. Compound ‘A’ is an acid and compound ‘B’ has a fruity smell. Suggest (i) chemical formulae and (ii) the structural formulae of compounds A and B. Name the functional group of compound B. What name would you give to the relationship between the compounds A and B. 3
(a) Two lenses have power of (i) + 2D (ii) - 4D. What is the nature and focal length of each lens.?

(b) An object is kept at a distance of 100cm from each of above lenses.

Calculate the (i) image distance (ii) magnification in each of the two cases. 3

Two elements X and Y belong to groups 1 and 2 respectively in the same period. Compare them with respect to

(a) the number of valence electrons

(b) valency

(c) metallic character

(d) size of the atoms.

(e) formulae of their oxides and chlorides. 3

(a) C₂H₆O is formula of second member of homologous series of alcohol. Give formula of fourth member.

(b)The molecular formula of an organic compound is C₃H₆O. Write the formula and names of aldehydes and ketones which are represented by this formula.

(c) What are structural isomers? Give all structural isomers of C₄H_10.

(a) Why does carbon form largest number of compounds?

(b) Why are some of these called saturated and other unsaturated compounds?

(c) Which of these two is more reactive and Why?

(d) Write the name and structure of two saturated and two unsaturated compounds. 5

In a household electric circuit different appliances are connected in parallel to one another.

Give two reasons.

An electrician puts a fuse of rating 5A in that part of domestic electrical circuit in which an electrical heater of rating 1.5kW, 220V is operating. What is likely to happen in this case and why? What change, if any, needs to be made?

You are given following current-time graphs from two different sources:

(i) Name the type of current in two cases.

(ii) Identify any one source for each type of these currents.

(iii) What is the frequency of current in case II in India?

(iv) Use above graphs to write two difference between the current in two cases. 5

SECTION B

What happens at the synapse between two neurons? 1
The human hand, cat paw and the horse foot, when studied in detail show the same structure of bones and point towards a common origin.

(i) What do you conclude from this?

(ii) What is the term given to such structures? 1

Name two gases, other than carbon-di-oxide, that are given out during burning of fossil fuel and contribute towards acid rain formation. 1
How did the ‘Chipko andolan’ ultimately benefit the local population? Give any two benefits. 2
Explain the Sex determination in Human. 2
Name those parts of the flower which serve the same function as the following do in the animals:-

(i) testis (ii) ovary (iii) eggs (iv) sperms. 2

Study carefully the food chains given below:-

Food chain I : grass - grasshopper - frog

Food chain II : wheat - rat - snake - hawk

To which of the two consumers, snake or hawk will more energy (percent) be available and why? 2

What do the following transport?

(i) xylem (ii) phloem (iii) pulmonary vein (iv) Vena Cava. 2

The genotype of green stemmed tomato plants is denoted as GG and that of purple stemmed tomato plants as gg. When these two are crossed,

(i) What colour of stem would you expect in their F1 progeny?

(ii) Give the percentage of purple-stemmed plants if F1 plants are self pollinated.

(iii) In what ratio would you find the genotypes GG and Gg in the F2 progeny?3

Why are environmentalists insisting upon ‘sustainable natural resource management’? Give any three reasons. 3
(i) Draw the diagram of heart and label its four chambers

(ii) Construct a table to show the functions of these four chambers. 5

Plants absorb water from the soil. How does this water reach the tree tops? Explain in detail.

papers sst

TIME-3 HOUR MAX.MARKS-80

Instructions :

Q1. Who were Nattukottai Chettiars?

What was the role of gomastha under the East India Company?

What was referred to as the ‘iron monster’ in London?

Q.2 Why was Vernacular Press Act passed in the year 1878? 1

Mention the main theme of ‘Oliver Twist’ written by Charles Dickens.

Q.3 Define a Patriarchal society. 1

Q.4 Describe the position of women in the field of central and state legislature. 1

Q.5 According to IUCN, define endemic species. 1

Q.6 In which two states of India Himalayan Yew is found? 1

Q.7 Give one main reason for low infant mortality rate in Kerala. 1

Q.8 State one reason behind tertiary sector becoming so important in India. 1

Q.9 Mention any one inconvenience in barter system. 1

Q.10 What is the meaning of liberalization? 1

Q.11 Describe any three significance of Salt march by Gandhiji. 3x1=3

Q.12 Describe any three impacts of the Non-cooperation movement over the towns and countryside in India. 3

Q13 Examine any two factors of the Economic Depression of 1929. What were its effects on USA? 2+1=3

Q.14 Read the following extract taken from the textbook and answer the questions that follow:

In 1926, Begum Rokeya Sakhawat Hossien, a noted educationist and literary figure.

strongly condemned men for withholding education from women in the name of religion

as she addressed the Bengal Women’s Education Conference:

The opponents of female education say that women will become unruly.....Fie! they call

themselves Muslims and yet go against the basic tenets of Islam which gives women an

equal right to education. If men are not led astray once educated, why should women?

(a) Explain how Begum Rokeya Sakhawat Hossein asserts women’s right to education?

(b) What was the impact of printed books on women in India in the 19th century.?1+2=3

Read the following passage and answer the questions given below it : 2+1=3

‘Dear children, don’t read these novels, don’t even touch them. Your life will be ruined. You will suffer disease and ailments. Why did the good Lord make you - to wither away at a tender age? To suffer in disease? To be despised by your brothers, relatives and those around you? No. No. You must become mothers; you must lead happy lives; this is the divine purpose. You, who were born to fulfill this sublime goal, should you ruin your life by going crazy after despicable novels?’

(a) Analyse the message given by the writer to children.

(b) Name the woman novelist of early nineteenth century who wrote against traditional role of women as wives and mothers.

Q.15 Why the power sharing is desirable? Describe with examples. Mention the prudential & moral cause for power sharing. 1+2

Q.16 What is democratic decentralization? Write any four major steps taken by the government in 1992 for the growth of Democratic decentralization in India. 1+2=3

Q.17 Mawsynram is the region of highest rainfall, yet it faces acute shortage of water. Why?3

Q.18 Compare India and Nepal on the basis of any three indicators of Human Development Index for 2004. 3

Q.19 In Britain the formation of the nation state was not the result of a sudden upheaval or revolution. It was the result of a long-drawn-out process. Explain. 4

Q.20 What are overlapping & cross-cutting differences? Describe with examples. 2+2=4

Q.21 Describe the types of political parties & their formation. 2+2=4

Q.22 Why is democracy better than dictatorship? Describe with examples how democracy is a form of government, which is accountable, responsive & legitimate. 1+3

Q.23 Compare the diagrams showing land use pattern of India and answer the questions that follow: 2+2

i) Name the two categories under which the area in use has increased. Give at least one reason for this increase.

ii) Name the two categories under which the area in use has decreased. Give at least one reason for this decrease.

Q.24 The growth rate in Agriculture is decelerating, which is an alarming situation. Explain. 4

Q.25 How are the activities in the economy classified on the basis of employment conditions? Explain. 4

Q.26 What is the basic idea behind the SHGs for the poor? Explain in your own words. 4

Q.28 Why is ‘tax’ on imports known as trade barriers? Why did the Indian Government impose barriers to foreign trade and foreign investments after Independence? Give three reasons. 1+3

Q.29 Six features with serial nos. 1 to 6 are marked on the given outline political map of India

Identify these features with the help of the following information and write their correct names on the lines marked in the map : 1X6

1. A city associated with Jallianwalan Bagh incident.

2. Place where the session of Indian National Congress was held in 1927

3. A type of soil

4. A major tea producing state.

5. An iron ore mine.

6. An oil field.

Locate and label the following on the given outline political map of India.

1. A place where session of Indian National Congress was held in September1920;

2. A place where Gandhi started satyagraha against Indigo planters.

3. A dam built on river Chenab.

4. An iron ore mine in Karnataka.

5. A natural gas field in Gujarat.

6. A thermal power plant in Tamilnadu.

clASS10TH

Class – X

Subject – Science (Theory)

Section A

1. Why pH scale limited to a fixed range. (1)

2. Give two safety measures, which will you, take while decomposition reaction of ferrous sulphate? (1)

3. Why does open time of key is more than its closed time.

4. Give principle on which electric fuse works.

MAGNETIC EFFECT OF CURRENT- Q and A

MAGNETIC EFFECT OF CURRENT

Why does a compass needle get deflected when brought near a bar magnet?

A compass needle is a small bar magnet. When it is brought near a bar magnet, its magnetic field lines interact with that of the bar magnet. Hence, a compass needle shows a deflection when brought near the bar magnet.

Draw magnetic field lines around a bar magnet.

Magnetic field lines of a bar magnet emerge from the north pole and terminate at the south pole. Inside the magnet, the field lines emerge from the south pole and terminate at the north pole, as shown in the given figure.

List the properties of magnetic lines of force.

The properties of magnetic lines of force are as follows.

(a) Magnetic field lines emerge from the north pole.

(b) They merge at the south pole.

(d) Magnetic lines do not intersect with each other.

Why don’t two magnetic lines of force intersect each other?

If two field lines of a magnet intersect, then at the point of intersection, the compass needle points in two different directions. This is not possible. Hence, two field lines do not intersect each other.

The magnetic field in a given region is uniform. Draw a diagram to represent it.

The magnetic field lines inside a current-carrying long straight solenoid are uniform.

Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.

Inside the loop = Pierce inside the table

Outside the loop = Appear to emerge out from the table

For downward direction of current flowing in the circular loop, the direction of magnetic field lines will be as if they are emerging from the table outside the loop and merging in the table inside the loop. Similarly, for upward direction of current flowing in the circular loop, the direction of magnetic field lines will be as if they are emerging from the table outside the loop and merging in the table inside the loop, as shown in the given figure.

Choose the correct option.

(d)The magnetic field inside a long, straight, current-carrying solenoid is uniform. It is the same at all points inside the solenoid.

When a proton enters in a region of magnetic field, it experiences a magnetic force. As a result of the force, the path of the proton becomes circular. Hence, its velocity and momentum change.

State Fleming’s left-hand rule.

Fleming’s left hand rule states that if we arrange the thumb, the centre finger, and the forefinger of the left hand at right angles to each other, then the thumb points towards the direction of the magnetic force, the centre finger gives the direction of current, and the forefinger points in the direction of magnetic field.

What is the principle of an electric motor?

The working principle of an electric motor is based on the magnetic effect of current. A current-carrying loop experiences a force and rotates when placed in a magnetic field. The direction of rotation of the loop is given by the Fleming’s left-hand rule.

Question 1:

Explain different ways to induce current in a coil.

The different ways to induce current in a coil are as follows:

(a) If a coil is moved rapidly between the two poles of a horse-shoe magnet, then an electric current is induced in the coil.

(b) If a magnet is moved relative to a coil, then an electric current is induced in the coil.

State the principle of an electric generator.

An electric generator works on the principle of electromagnetic induction. It generates electricity by rotating a coil in a magnetic field.

Name some sources of direct current.

Some sources of direct current are cell, DC generator, etc.

Which sources produce alternating current?

AC generators, power plants, etc., produce alternating current.

Choose the correct option.

Name two safety measures commonly used in electric circuits and appliances.

Two safety measures commonly used in electric circuits and appliances are as follows:

(i) Each circuit must be connected with an electric fuse. This prevents the flow of excessive current through the circuit. When the current passing through the wire exceeds the maximum limit of the fuse element, the fuse melts to stop the flow of current through that circuit, hence protecting the appliances connected to the circuit.

(ii) Earthing is a must to prevent electric shocks. Any leakage of current in an electric appliance is transferred to the ground and people using the appliance do not get the shock.

Question 2:

An electric oven of 2 kW is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.

Current drawn by the electric oven can be obtained by the expression,

P = VI

Where,

Current = I

Power of the oven, P = 2 kW = 2000 W

Voltage supplied, V = 220 V

Hence, the current drawn by the electric oven is 9.09 A, which exceeds the safe limit of the circuit. Fuse element of the electric fuse will melt and break the circuit.

Question 3:

What precaution should be taken to avoid the overloading of domestic electric circuits?

The precautions that should be taken to avoid the overloading of domestic circuits are as follows:

(a) Too many appliances should not be connected to a single socket.

(b) Too many appliances should not be used at the same time.

(d) Fuse should be connected in the circuit.

Question 1:

Which of the following correctly describes the magnetic field near a long straight wire?

(d) The magnetic field lines, produced around a straight current-carrying conductor, are concentric circles. Their centres lie on the wire.

Question 2:

The phenomenon of electromagnetic induction is

(c) When a straight coil and a magnet are moved relative to each other, a current is induced in the coil. This phenomenon is known as electromagnetic induction.

Question 3:

(a) An electric generator produces electric current. It converts mechanical energy into electricity.

(c) When two naked wires of an electric circuit touch each other, the amount of current that is flowing in the circuit increases abruptly. This causes short-circuit.

An electric motor converts electrical energy into mechanical energy.

A generator is an electric device that generates electricity by rotating a coil in a magnetic field. It works on the principle of electromagnetic induction.

A long circular coil is a long solenoid. The magnetic field lines inside the solenoid are parallel lines.

Live wire has red insulation cover, whereas earth wire has green insulation colour in the domestic circuits.

Question 7:

List three sources of magnetic fields.

Three sources of magnetic fields are as follows:

(a) Current-carrying conductors

(b) Permanent magnets

Question 8:

How does a solenoid behave like a magnet? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.

A solenoid is a long coil of circular loops of insulated copper wire. Magnetic field lines are produced around the solenoid when a current is allowed to flow through it. The magnetic field produced by it is similar to the magnetic field of a bar magnet. The field lines produced in a current-carrying solenoid is shown in the following figure.

In the above figure, when the north pole of a bar magnet is brought near the end connected to the negative terminal of the battery, the solenoid repels the bar magnet. Since like poles repel each other, the end connected to the negative terminal of the battery behaves as the north pole of the solenoid and the other end behaves as a south pole. Hence, one end of the solenoid behaves as a north pole and the other end behaves as a south pole.

Question 9:

When is the force experienced by a current-carrying conductor placed in a magnetic field largest?

The force experienced by a current-currying conductor is the maximum when the direction of current is perpendicular to the direction of the magnetic field.

Question 10:

Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?

The direction of magnetic field is given by Fleming’s left hand rule. Magnetic field inside the chamber will be perpendicular to the direction of current (opposite to the direction of electron) and direction of deflection/force i.e., either upward or downward. The direction of current is from the front wall to the back wall because negatively charged electrons are moving from back wall to the front wall. The direction of magnetic force is rightward. Hence, using Fleming’s left hand rule, it can be concluded that the direction of magnetic field inside the chamber is downward.

Question 10:

Question 13:

A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (i) pushed into the coil, (ii) withdrawn from inside the coil, (iii) held stationary inside the coil?

A current induces in a solenoid if a bar magnet is moved relative to it. This is the principle of electromagnetic induction.

(i) When a bar magnet is pushed into a coil of insulated copper wire, a current is induced momentarily in the coil. As a result, the needle of the galvanometer deflects momentarily in a particular direction.

(ii) When the bar magnet is withdrawn from inside the coil of the insulated copper wire, a current is again induced momentarily in the coil in the opposite direction. As a result, the needle of the galvanometer deflects momentarily in the opposite direction.

(iii) When a bar magnet is held stationary inside the coil, no current will be induced in the coil. Hence, galvanometer will show no deflection.

Question 14:

Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.

Two circular coils A and B are placed close to each other. When the current in coil A is changed, the magnetic field associated with it also changes. As a result, the magnetic field around coil B also changes. This change in magnetic field lines around coil B induces an electric current in it. This is called electromagnetic induction.

Question 15:

State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current, (ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (iii) current induced in a coil due to its rotation in a magnetic field.

(i) Maxwell’s right hand thumb rule

(ii) Fleming’s left hand rule

(iii) Fleming’s right hand rule

Question 16:

When does an electric short circuit occur?

If the resistance of an electric circuit becomes very low, then the current flowing through the circuit becomes very high. This is caused by connecting too many appliances to a single socket or connecting high power rating appliances to the light circuits. This results in a short circuit.

When the insulation of live and neutral wires undergoes wear and tear and then touches each other, the current flowing in the circuit increases abruptly. Hence, a short circuit occurs.

Question 18:

What is the function of an earth wire? Why is it necessary to earth metallic appliances?

The metallic body of electric appliances is connected to the earth by means of earth wire so that any leakage of electric current is transferred to the ground. This prevents any electric shock to the user. That is why earthing of the electrical appliances is necessary.

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