CBSE Half Yearly Sample Paper 2020-21 Science for class 10
Time: 3:00 hour
All questions are compulsory.
1- Multiple choice Questions: 7
i) If four resistors, each of 4 ohm resistance are joined in parallel arrangement, what is the effective resistance of the combination?
a) 16 ohm
b) 4 ohm
c) 1 ohm
d) 1/4 ohm
ii) Electrical resistivity of a given metallic wire depends upon
a) its length
b) it’s thickness
c) its shape
d) the nature of its material
iii) Which of the following is not attracted by a bar magnet?
a) soft iron
iv) Direction of induced current is determined by applying
a) Fleming’s left hand rule.
b) Fleming’s right hand rule
c) right hand thumb rule
d) clock facing rule
v) The laws of reflection hold good for
a) plane mirror only
b) concave mirror only
c) convex mirror only
d) all mirrors irrespective of their shape
vi) Magnification produced by a rear view mirror fitted in vehicles.
a) is less than 1
b) is more than one
c) is equal to 1
d) Can be more than or less than 1 depending upon the position of object in front of it.
vii) The image formed by convex mirrors for any position of an object placed in front of mirror is.
a) Virtual and erect
b) Situated between pole and principal focus of mirror
c) Diminished in size
d) having all these characteristics
2- Answer the following questions. (6)
i) In the circuit below resistors R1 and R2 are in parallel and have resistances of 8 Ω and 4 Ω, respectively. The current passing through R1 is 0.2 A. Find the voltage across resistor R2 and the current passing through the same resistor.
ii) What is an electromagnet list any two uses of electromagnet?
iii) What are the characteristics of good fuel?
3- Answer these questions in detail:- (6)
i) How will the strength of magnetic field at a point around a current carrying conductor change when the (a) Current in the conductor is increased (b) Direction of current is reversed (c) Distance of the point is increased.
ii) How does a concave mirror converge a parallel beam of light ray, explain with a suitable diagram. Mark and define pole principal focus and centre of curvature of a concave mirror in the diagram.
4- Answer this question:- (4)
i) Which is the better way to connect light and other appliances in domestic circuit, series connection or parallel electrical connection? Justify your answer.
ii) Electrician has made electric circuit of a house in such a way that if a lamp gets used in a room of house, all the lamps in other rooms of the house stop working .what is the defect in this type of circuit wiring? Give reason.
5- Study the following situation and answer the questions that follow: (5)
A spherical mirror produces an image 48 cm in front of it when an object is placed at a distance of 12 cm from its pole. Calculate the focal length of the mirror and answer the following questions:
i) Identify the nature of mirror
ii) Will the image be magnified or diminished
iii) Will the image formed be erect or inverted? Also make a ray diagram.
1- 1 mark questions.
i) Why are carbon and its compound used as fuel for most application?
ii) What are the two properties of Carbon which lead to a large number of carbon compounds we see around us?
iii) What is Homologous series? Which two of the following organic compounds belong to the same homologous series?
C2H6, C2H6, C2H6O2, CH4O
2- 2 Marks questions.
i) Write the main difference between the properties of diamond and graphite.
ii) Which gas is produced when dil hydrochloric acid is added to a reactive metal? Write the chemical equations when iron reacts with dil H2SO4.
iii) What would you observe when zinc is added to a solution of iron (II) sulphate?
3- Compounds such as alcohol and glucose also contain hydrogen but are not categorised as acids. Describe an activity to prove it.
4- A metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
5 (i)- A Shiny brown coloured metal X on heating in a China dish becomes black in colour. (a) Name the metal X and the black colour compound formed. (b) Write the balanced chemical equation of the reaction that takes place.
5 (ii) -Identify the substance oxidized substance reduced oxidizing agent and reducing agent in the following reaction. MnO2+ 4 HCl ——— MnCl2 + Cl2 + 2H2O
6- Why do ionic compounds have high melting points?
7- Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
8- Give electron dot structure and structural formula of the third member of alkenes and fifth member of alkenes series.
9- Give reason unsaturated hydrocarbon show addition reactions but saturated hydrocarbons do not.
1- The flow of energy in an ecosystem is always-
2- The sexually transmitted disease which is caused by bacteria is-
3- The blood vessel which carries oxygenated blood from lungs to the heart is-
a) Cardiac artery
b) Pulmonary Vein
c) Main artery
d) Pulmonary artery
4- There are two statements given, one labelled Assertion(A) and other labelled Reason (R).Select the correct answer from the alternatives given below-
Assertion-Top carnivores also get energy from the plants indirectly.
Reason-Plants changethe solar energy into chemical energy and stored in the food synthesized.
a) A is false and R is true.
b) A is true but R is false.
c) A and R both are true
d) A is completely correct but R is partially correct.
5- What are the various steps of food chain called?
6- What are the names of asexual reproduction methods occurred in spirogyra and yeast?
7- Name the two waste products produced in human body cells.
8- Which organisms of the following belong to the same trophic level? Spider, deer, plants, hawk and rat
9- Define the vegetative propagation. Name the parts of the given plants by which they reproduce by vegetative propagation.
10- Name the tissues in plants that transport water and minerals. Name the two cells of this tissue and state whether these cells are living or dead.
11- Write the full name of C.F.C. Mention its effects on our environment.
Explain how harmful chemicals enter our body.
12- Draw a neat and well-labelled diagram of a plant or human.
13- What type of respiration takes place in human muscles during vigorous physical exercise? Give reason for your answer and its end product.
Name the parts of plants through which they respirate.
14 (a) What is photosynthesis? Write the chemical reaction to show the photosynthesis in plants.
14 (b) Draw a well-labelled diagram of human digestive system.
14 (a) Write the full form of the following abbreviations-
i) I U C D
ii) S T D
iii) O C
14 (b) Draw a well-labelled diagram of embryo of gram seed.