St.

Kabir’s School
Preboard Examination
Session 2022-23
Class X
Physics
Time-2 hrs. MM 80

General Instructions

.You will not be allowed to write during the first 15 min. This time is to be spent
in reading the question paper .

. The time given at the head of the paper is the time allowed for writing the
answers.

.Attempt all questions from Section A and any 4 questions from section B

.The intended marks for questions or parts of questions are given in brackets [ ]

Section –A

[Attempt all questions ]

1. Choose the correct answers to the questions from the given options.

(i) The quantity torque is also known as

(a) moment of momentum (b) moment of velocity

(c) moment of force (d) moment of direction

(ii) A body of mass 0.5 kg travels in a straight line with velocity v=ax 3/2 , where a =5ms-2. What is
the work done by the net force during its displacement from x=0 to x = 2 m ?

(a) 150 J (b) 100 J (C) 50 J (d) 200 J

(iii)In a bell ring of cycle , the conversion of energy takes place from

(a) elastic to light (b) light to mechanical (c) mechanical to sound (d) sound to elastic

(iv) The nuclear radiation which gets deflected towards negatively charged plate in an electric
field is

(a) gamma (b) ultraviolet (c) beta (d) alpha

(v) If a swimmer inside water looks at an aeroplane in the sky, then which of the following
conditions are fulfilled ?
(a) For the swimmer, the aeroplane will appear to be lower than it actually is.

(b)For the swimmer, the aeroplane will appear to be higher than it actually is .

(c) For the swimmer, the aeroplane will appear as its actual height.

(d) For the pilot , the swimmer will appear to be at greater depththan it actually is .

(vi) For an object placed between F1 and 2F1, the correct ray diagram is

(vii) An opera singer breaks the wine glass with her voice alone . It is a consequence of

( a) shrillness of sound (b) loudness of sound (c) resonance (d) interference

(viii) A cell, a resistor, a key and ammeter are arranged as shown in the circuit diagrams of
figure (i), (ii) and (iii). The current recorded in the ammeter will be

(a) maximum in (i) (b) maximum in (ii) (c) maximum in (iii) (d) same in all of these

(ix) A long straight current carrying wire produces magnetic field as given below
If the wire is curled up wounded over a pencil, the magnetic field would take shape as of

(a) bar magnet (b) circular magnet (c)U- shaped magnet (d)circles

(x)An electric kettle with a 2 kW heater contains 0.25 kg of boiling water. It will take time of
______

Before all the water to boil away.

( Take specific latent heat for steam = 2MJ/kg)

(a) 250 s (b) 400 s (c) 600 s (d) 850 s

(xi) For TIR, the refractive index is equal to

(a) sinic (b) cosic (c) cosec ic (d) sec ic

(xii) For cooking of food , which of the following type of utensil is most suitable ?

(a) High specific heat and low conductivity(b) High specific heat and high conductivity

(c) Low specific heat and low conductivity(d) Low specific heat and high conductivity

(xiii) The raindrops fall on the ground. It has maximum kinetic energy at

(a) surface of the earth(b)just leaving the clouds

(c) mid-way between the earth and cloud (d) None of above

(xiv)Beams of light are incident through the holes A and B emerge out of box through the
holes C and D respectively as shown in figure. Which of the following could be inside the box ?
(a) A rectangular glass slab (b) A convex lens (c) A concave lens (d) A prism

(xv) Direction of force on a current carrying conductor placed perpendicular to magnetic field
will be

(a) upward or downward to the magnetic field and wire

(b) right or left (c) in the direction of current (d) None of the above

Q2 (a)(i) Name the type of single pulley that can act as a force multiplier. Draw a labelled

diagram of the above named pulley . [1]

(b) What is meant by nuclear waste? [1]

(c) What are the sources of harmful radiatios ?[1]

(ii) (a) In figure, a roller of diameter 0.2 m is raised on the pavement AB by the forces F 1 and F2

each of magnitude 20 N. Compare the torques produced by the two forces . [1]

(b) What is the direction of force F2? [1]

(iii) Observe the given figure and write the location of centre of gravity for both objects. [2]
(iv) A body of mass 1.5 kg is dropped from second floor of a building which is at a height of 12
m. What is the force acting on it during its fall? (Take g= 9.8 ms -2) [2]

(v) A half meter ruler is suspended by a thread from the mid-point of the ruler as shown in the
figure. It balances horizontally when a 50 g and an unknown weight was suspended
respectively from 10 cm and 45 cm mark .Calculate the magnitude of weight w.[2]

(vi)(a) Calculate the value of the resistance which must be connected to a 15 Ω resistance to
provide an effective resistance of 6 Ω. [1]

(b)What is the colour code for the insulation on the earth wire? [1]

(vii)(a) What is the name given to atoms a substance which have the same atomic number but
different mass number? [1]

(b) What is the difference in the atomic structure of such atoms? [1]

Q3.(i) A lens cannot form an image on the screen .

(a)Name the lens. [1]

(b) Name the nature of the image .[1]

(ii) An electric geyser rated 150 W, 250 V is connected to a 250 V line mains. Find

(a)the electric current drawn by it. [1]

(b)energy consumed by it in 50 h. [1]

(iii)A straight conductor passes vertically through a cardboard having some iron fillings
sprinkled on it. What changes occur if

(a)strength of current is increased ? [1]

(b)the single conductor is replaced by several parallel conductors each carrying same
current flowing in the same direction ? [1]
(iv) Water is used in cold countries as heat reservoir for wine and juice bottles to prevent their
freezing. Why ? [2]
(v) (a) Name the radiations which does not effect the mass number and atomic number of
parent nuclei during radioactive disintegration. [1]
(b) Complete the following reaction by filling the gaps.

Na [1]

Section –B
 [Attempt any four questions ]

Q 4. (i) (a) We can burn a piece of paper by focussing the sun rays by using a convex lens. Draw
a ray diagram to show this phenomenon. [1]
(b) Study the diagram given below [2]

I. State two characteristics of the image formed .

II. What are the points O and O’ called?

(ii) (a) How are angle of incidence and angle of emergence related when prism is in the position
of minimum deviation ? [1]
(b) The critical angle for material of which the equiangular prism ABC (shown in figure)is
made , is of 60o . A ray of light incident on the side AB of the prism is refracted along DE
such that the angle it makes with the side AC is 150o.Also EDB =90o . Draw the path of the
incident ray on the side AB ( which travels along DE) and also the path which the ray DE
travels from point E onwards. [2]

(iii) (a) How does the power of a convex lens vary , If the incident violet light is replaced by
red light ? [1]
(b) What type of lens is an air bubble inside water ?[1]

(c) Name the subjective property of light related to its wavelength .[1]

(d) What is the relation between focal length and radius of curvature ?[1]

Q 5.(i) (a) Explain, why strings of different thickness are provided on a stringed instrument . [1]

(b) A man standing between two cliffs produces a sound and hears two successive
echoes at intervals of 2 s and 5 s, respectively. Calculate the distance between the two
cliffs . The speed of sound in air is 330 ms-.[2]

(ii) Arrange α, β andϒ rays in ascending order w.r.t their

(a) penetrating power (b) ionising power (c ) biological effect [3]

(iii) (a) Why is the ratio of velocities of light of wavelength 2500 Aoand 5000 Ao in vacuum
1:1? [1]
(b) In which region both the wavelength lies? [1]

(c) Which of the above wavelength has a higher frequency ? [1]

(d)A wave has a frequency of 800 MHz and wavelength of 30 cm . Calculate velocity ?
[1]
o o
Q 6.(i) (a) Which contains more heat , 1 kg water at 100 C or 1 kg steam at 100 C ? [1]

(b)Name a substance that contracts on melting and expands on solidification .[1]

 (c) Why does the heat supplied to a substance during its change of state not cause any
rise in its temperature ? [1]
(ii) A vessel of negligible thermal capacity contains 5 kg of water at 50 C . If 5.0 kg of ice at 0o
o

C is added to it, find

(a)heat energy imparted by water in fall of its temperature from 50 o C to 0o C . [1]

(b)mass of ice melted and [1]

(c)final temperature of mixture . Given , specific heat capacity of water =4200 J kg -1 K-1,
specific latent heat of ice = 336 kJ kg-1 . [1]
(iii) The figure shows a magnetic needle keep just below the conductor AB which is kept in
North- South direction .

(a) In which direction will the needle deflect when the key is closed ? [1]

(b) Why is the deflection produced? [1]

(c) What will be the change in the deflection , if the magnetic needle is taken just
above the conductor AB ? [1]
(iv) Name one device which works on this principle . [1]

Q 7(i) A pulley system with VR =4 is used to lift a load 175 kgf through a vertical height of 15 m.
The effort required is 50 kgf in the downward direction. (Take g= 10 ms -2).
Calculate

(a)distance moved by the effort. [1]

(b)mechanical advantage of the pulley system . [1]

(c)efficiency of the pulley system . [1]

(ii)(a) How can a beam balance comes to static equilibrium ? [1]

(b)A force applied on a

(1) rigid body (11) non-rigid body

How does the effect of force differ in the two cases ? [2]

(iii) (a) Calculate the work done when

I. A 20 kg weight is lifted 2 m vertically.

 II.a bike is moved on a rough road through 35 m against a frictional resistance of 20
N .g= 9.8ms-2 [2]

(b) What is the work done by a force when the force is

I.normal to the displacement produced .

II.in the same direction as the displacement produced ?[2]

Q 8.(i) Three resistors of 6.0 Ω, 2.0 Ω and 4.0 Ω respectively are joined together as shown in the
figure. The resistors are connected to an ammeter and to a cell of emf 6.0 V

Calculate

(a)the effective resistance of the circuit.

(b)the current drawn from the cell. [3]

(ii) (a) What are background radiations ? [1]

(b)Write an equation of an α- emission from U . [1]

(c) What will be the change in the rate of radioactivity, if the temperature of the
radioactive substance is raised to four times the initial temperature ?[1]
(iii) (a) Name the new and odd colour codes of the wire which is connected to the switch

of an appliance . [2]

(b)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) held stationary inside the coil ?[2]

Q 9.(i) The melting point of naphthalene is 80 o C and the room temperature is 30 o C. A sample
of liquid naphthalene at 100 o C is cooled down to the room temperature . Draw a
temperature- time graph to represent this cooling. In this graph, mark the region which
corresponds to the freezing process. State the forms of naphthalene from the graph.
[3]
(ii)A metal present at 120 o C is quickly dropped in a calorimeter of mass 80 g containing
200 g of water at 30 o C. The final temperature attained by the mixture is 40 oC .
Calculate the thermal capacity of the metal piece. [ Specific heat capacity of water= 4.2
 J g-1oC-1, specific heat capacity of calorimeter = 0.4 J g-1o C-1 ]
[3]
(iii) (a) A narrow beam of white light is passing through a glass prism ABC as shown in the

diagram

Trace it on your answer sheet and show the path of the emergent beam as observed on
the screen DE.

(I) Write the name and cause of phenomenon observed .

(II) Where else in nature is this phenomenon observed ?[2]

(b) The figure below shows the displacement-time graph two sound waves in air.

(I) Which wave will have greater loudness and why ?

(II) What is the ratio of frequency of (I) and (II) [2]