REVISION EXAMINATION, NOVEMBER 2020
Class X
Time Allowed: 2 hours
Maximum Mark : 50
Subject : Science
Date : 30.11.2020
Name :……………………………………..Sec:-…….Roll No ............ Total no. of pages : 5
GENERAL INSTRUCTIONS:
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Physics ,Chemistry &Biology to be written in separate answer sheets
Your name and roll no has to be written in all the three answer sheets.
Answer sheets has to be uploaded as three separate PDF file.
Keep your hardcopy safe.
PHYSICS
1. Redraw the diagram given below in your answer sheet and show the direction of the light ray after
refraction from the lens.
(1)
For questions 2 and 3,two statements are given- one labeled Assertion(A) and the other labeled
Reason(R).Select the correct answer to these questions from the codes a,b,c and d as given
below.
a)
b)
c)
d)
Both A and R are true, and R is the correct explanation of the assertion.
Both A and R are true, R is not the correct explanation of the assertion.
A is true but R is false.
A is false but R is true.
2. Assertion: Sun appears over the horizon two minutes before the actual sunrise.
Reason: Light has to travel a larger distance in the atmosphere during sunrise.
(1)
3. Assertion: In Fleming’s left hand rule, the direction of magnetic field, force and current are
mutually perpendicular.
Reason: Fleming’s left hand rule is applied to measure the induced current.
(1)
4. For the given data showing the focal lengths of three concave mirrors A, B and C and the respective
distances of different objects from these mirrors.
(2)
S.No
A
B
C
Object
distance(cm)
50
30
20
Focal length(cm)
20
15
30
In the given position of the object from the mirrors, which mirror form a diminished image of the
object .Draw ray diagram for the formation of image by this mirror.
5. With the help of a diagram of experimental set up describe an activity to show that the force acting on
a current carrying conductor placed in a magnetic field increases with increase in field strength.
(2)
6. Read the following and answer any three questions from 6(i) to 6(iv)
(1x3=3)
Lenses are objects made of transparent materials such as glass or plastic that has curved surfaces. There
are two main kinds of lenses-Diverging and Converging lenses. Magnifying glasses, microscopes and
some types of telescopes use converging lenses to make small things appear much larger or to make
distant object appear much closer. Converging lenses magnify by bending the rays of light that pass
through them to meet at a point. This point is called a focus. The thicker that a converging lens is in its
centre, the more it magnifies and the closer the focus is to the lens.
The magnifying power of a single converging lens such as that used in a camera or magnifying glass is
equal to the length of the enlarged image divided by the length of the original object. For example ,if a
2cm long beetle appears to be 6cm long when viewed through a magnifying glass, the glass magnifying
power is 3(written as ‘’3x’’).Similarly, a 10x lens would make an object look 10 times longer. It will
also look 10 times wider.
i)What happens to the focal length of the convex lens when it is cut horizontally?
ii)Explain why you cannot measure the focal length directly for a diverging lens.
iii)When seen through a 3x magnifying glass, a small leaf appears to have an area of 9mm2. What is
the actual area of the leaf?
iv)Calculate the distance at which an object from a converging lens of focal length 10cm be placed
to obtain an image of double the size.
7. An electric heater consumes 4.2 units of electrical energy per hour of its use. It is designed to work on
the mains of 220V.
(5)
a) What is the power rating of this device?
b) What is the resistance of this device?
c) Does the resistance of this device remain constant during its operation?
d) What is the current flowing through this device when it is connected across the mains?
e) Cost of energy consumed if each unit cost is Rs.5.
OR
a) Compass needle is placed near a current-carrying wire. State your observation for the
following cases, and give reason for the same in each casei) Magnitude of electric current in the wire is increased.
ii) The compass needle is displaced away from the wire.
b) A steady current of 5A is flowing through a conductor AB. Will the current be induced in the
circular wire of radius 1m?
5A
A
B
c) A positively charged particle X and a negatively charged particle Y are moving
perpendicular to uniform magnetic field at some instant of time.
Find the direction of magnetic force acting on the charged particle at this instant.
CHEMISTRY
MULTIPLE CHOICE QUESTIONS
1. What happens when calcium is treated with water?
(i) It does not react with water
(ii) It reacts violently with water
(iii) It reacts less violently with water
(iv) Bubbles of hydrogen gas formed stick to the surface of calcium
(a) (i) & (iv)
(b)
(ii)& (iii)
(c)
(i) & (ii)
2. The second member of alkyne homologous series is
(a) Ethyne
(b) Propyne
(c) Ethene
(d)
(1)
(iii)&(iv)
(1)
(d) Ethane
For question numbers 3 and 4 two statements are given one labelled Assertion (A) and other labelled
Reason (R). Select the correct answer to these questions from codes 𝑎, 𝑏, 𝑐, 𝑎𝑛𝑑 𝑑 given below.
(a)
Both 𝐴 𝑎𝑛𝑑 𝑅 are true and 𝑅 is the correct explanation of the assertion.
(b)
Both 𝐴 𝑎𝑛𝑑 𝑅 are true and 𝑅 is not the correct explanation of the assertion.
(c)
𝐴 is true but 𝑅 is false.
(d)
𝐴 is false but 𝑅 is true.
3. Assertion: Ferrous sulphate crystals are green in colour, but on heating they first turn white and on
further heating decomposes to leave behind a reddish brown residue.
Reason: They turn white due to loss of water on crystallisation and the reddish brown residue is due
to formation of 𝐹𝑒2𝑂3.
(1)
4. Assertion
:
All salts form neutral solution with 𝑃𝐻 = 7
Reason
:
Salts are formed by neutralisation of an acid with a base.
(1)
5. (a) Explain the formation of calcium chloride with the help of electron dot structure. (Atomic
numbers: 𝐶𝑎 = 20, 𝐶𝑙 = 17)
(2)
(b) Why do ionic compounds have high melting point?
6. (a) Write the chemical name and chemical formula of washing soda.
(3)
(b) How is it obtained from sodium chloride? Give equations for the reaction.
(c) How does the concentration of hydronium ion [𝐻3 𝑂+ ] change when a solution of an acid is
diluted?How does it affect the pH of the solution?
7. (a) What are the two properties of carbon which lead to huge number of carbon compounds we see
around us?
(3)
(b) Write the name and structure of a saturated compound in which the carbon atoms are arranged
in a ring. Give the number of single bonds present in this compound.
(c) Write the IUPAC name of the following compounds. (i)
𝐶𝐻3 − 𝐶𝐻2 − 𝐶𝐻2 − 𝐶 ≡ 𝐶𝐻
(ii) 𝐶𝐻3 − 𝐶𝐻 − 𝐶𝐻3
CH3
8. Study the following table in which positions of six elements 𝑃, 𝑄, 𝑅, 𝑆, 𝑇 𝑎𝑛𝑑 𝑈 are shown as they are in
the modern periodic table:
(3)
Group
1
2
3 – 12
13
14
15
16
17
18
→
Period ↓
2
3
P
Q
S
T
On the basis of the above table, answer the following questions:
a)
b)
c)
d)
e)
Name the element which forms only covalent compounds
Name the element which is a metal with valency three.
Name the element which is a non – metal with valency three.
Out of S and T which is bigger in size and why?
Write the common name for the family to which the elements R and U belong.
R
U
BIOLOGY
1. Why do humans and birds have double circulation?
(1)
2. In a food chain comprising Grass, Grasshopper, Frog, Snake and Hawk, suppose the amount of energy
at fourth trophic level is 5 kJ, what will be the energy available at the producer level?
(1)
3. More complex organisms cannot give rise to new individuals through regeneration. Why? (1)
4. For the following question, two statements are given- one labeled Assertion
(A) and the other labeled Reason (R). Select the correct answer to these questions from the codes
(a), (b), (c) and (d) as given below:
a) Both A and R are true, and R is correct explanation of the assertion.
b) Both A and R are true, but R is not the correct explanation of the assertion.
c) A is true, but R is false.
d) A is false, but R is true.
Assertion: Surgical methods are very effective and permanent methods of contraception which
can be adopted by a male or a female.
Reason: Surgical methods can be used to create blocks in the reproductive tracts of a male or a
female to prevent pregnancy and are also effective in preventing sexually transmitted diseases.
(1)
5. Read the following and answer any three questions from (i) to (iv) .
(3x1)
The biological process involved in the removal of the harmful metabolic wastes from the body is
called excretion. Different organisms use varied strategies to do this.
(i) The excretory system of human beings include
a) a pair of kidneys, a ureter, a urinary bladder and a urethra.
b) a pair of kidneys, a pair of ureters, a urinary bladder and a urethra.
c) a pair of kidneys, nephrons, renal artery and renal vein.
d) a pair of kidneys, a pair of ureters and a urinary bladder.
(ii) The four substances that are selectively reabsorbed as the urine flows along the renal
tubule are
a) glucose, amino acids, urea and water
b) amino acids, salts, water and glucose
c) glucose, amino acids, vitamins and water
d) glucose, salts, water and minerals
(iii) Study the table below and select the row that has the incorrect information
Alveoli
(a) Tiny air sacs present in lungs
(b) The walls of alveoli are one cell thick and it
contains an extensive network of blood
capillaries.
(c) The exchange of oxygen and carbon dioxide
takes place between the blood of the
capillaries that surround the alveoli and
gases present in the alveoli.
(d) The exchange of gases takes place through
the walls of alveoli by diffusion.
Nephrons
Tiny tubular structures present in the
kidneys
Nephrons are made up of glomerulus,
Bowman’s capsule and a long renal tubule.
The blood enters the kidneys through the
renal vein and the nitrogenous waste
materials in the form of urine is collected
bycollecting duct.
The waste materials are removed in the
nephrons by filtration, re-absorption and
secretion.
(iv) Choose the incorrect statement from the following:
a) An artificial kidney is a devise to remove nitrogenous waste products through dialysis.
b) Normally in a healthy adult, the initial filtrate in the kidneys is 1 litre per day. c ) The
volume of urine excreted is only a litre or two a day.
d) Excretion and osmoregulation are the two major functions of kidneys.
6. What is the significance of stratospheric ozone layer? How does it get depleted?
(2)
7. Leaves of a healthy potted plant were coated with Vaseline to block the stomata. Will this plant
remain healthy for long? State three reasons for your answer.
OR
What are the different ways in which glucose is oxidized to provide energy in various organisms? (3)
8. A blue colour flower plant denoted by BB is crossbred with that of white colour flower plant
denoted by bb.
a) State the colour of flower you would expect in their F1 generation plants.
b) What must be the percentage of white flower plants in F2 generation if flowers of F1 plants
are self-pollinated?
c) State the expected ratio of the genotypes BB and Bb in the F2 progeny.
(3)
9. a) Explain the process of double fertilization in flowering plants with the help of a labeled diagram.
b) What is a bisexual flower? Give one example.
OR
a) Why is pollination a pre-requisite for fertilization in plants?
b) What are the post-fertilization events in plants?
c) Draw a diagram showing the structure of a germinating dicot seed.
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(5)