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MODEL PAPER 9 Physics - MODEL PAPER 9

CBSE - STD 12 Science - Physics (CBSE - English Medium). 38 questions in this chapter.

Question types

MODEL PAPER 9 question types

38 questions across 6 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

38
Questions
6
Question groups
5
Question types
Sample Questions

MODEL PAPER 9 questions

One sample from each question group in this chapter. Select any group above to see the full set with answer keys.

Q 1M.C.Q (1 Marks)1 Mark
How will the image formed by a convex lens be affected if the central portion of the lens is wrapped in a black paper?
  • A
    No image is formed by the remaining portion of the lens
  • B
    Full image will be formed but will be less bright
  • C
    Two images will be formed
  • D
    Central portion of the image will be absent
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Q 2M.C.Q (1 Marks)1 Mark
In the given figure, a diode D is connected to an external resistance $R =100 \Omega$ and an emf of 3.5 V . If the barrier potential developed across the diode is 0.5 V , the current in the circuit will be
Image
  • A
    40mA
  • B
    30mA
  • C
    35mA
  • D
    20mA
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Q 3M.C.Q (1 Marks)1 Mark
A semi$-$circular arc of radius $'a\ '$ is charged uniformly and the charge per unit lengths is $\lambda$. The electric field at the centre is:
  • A
    $\frac{\lambda}{2 \pi \varepsilon_0 a^2}$
  • B
    $\frac{\lambda}{4 \pi \varepsilon_0 a}$
  • ✓
    $\frac{\lambda}{2 \pi \varepsilon_0 a}$
  • D
    $\frac{\lambda^2}{2 \pi \varepsilon_0 a}$

Answer: C.

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Q 4M.C.Q (1 Marks)1 Mark
In Young's double$-$slit experiment, the intensity of light at a point on the screen where the path difference is $\lambda$ is $k ( \lambda$ being the wavelength of light used$).$ The intensity at a point where the path difference is $\frac{\lambda}{4}$, will be
  • A
    $k$
  • B
    $\frac{k}{4}$
  • ✓
    $\frac{k}{2}$
  • D
    zero

Answer: C.

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Q 5M.C.Q (1 Marks)1 Mark
The susceptibility of a magnetic substance is found to depend on temperature and the strength of the magnetising field. The material is a:
  • A
    diamagnet
  • B
    superconductor
  • C
    ferromagnet
  • D
    paramagnet
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Q 6Assertion (A) & Reason (B) MCQ1 Mark
Assertion (A): The dc and ac both can be measured by a hot wire instrument.
Reason (R): The hot wire instrument is based on the principle of magnetic effect of current.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • C
    A is true but R is false.
  • D
    A is false but R is true.
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Q 7Assertion (A) & Reason (B) MCQ1 Mark
Assertion (A): In Young’s double-slit experiment if wavelength of incident monochromatic light is just doubled, number of bright fringe on the screen will increase.
Reason (R): Maximum number of bright fringe on the screen is inversely proportional to the wavelength of light used.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • C
    A is true but R is false
  • D
    A is false but R is true.
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Q 8Assertion (A) & Reason (B) MCQ1 Mark
Assertion: Positive charge always moves from a higher potential point to a lower potential point.
Reason: Electric potential is a vector quantity.
  • A
    Assertion and reason both are correct statements and reason is correct explanation for assertion.
  • B
    Assertion and reason both are correct statements but reason is not correct explanation for assertion.
  • C
    Assertion is correct statement but reason is wrong statement.
  • D
    Assertion is wrong statement but reason is correct statement.
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Q 9Assertion (A) & Reason (B) MCQ1 Mark
Assertion (A): In photoemissive cell inert gas is used.
Reason (R): inert gas in the photoemissive cell gives greater current.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • C
    A is true but R is false.
  • D
    A is false but R is true.
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Q 102 Marks Questions2 Marks
A deuteron and an alpha particle having same momentum are in turn allowed to pass through a magnetic field $\vec{B}$, acting normal to the direction of motion of the particles. Calculate the ratio of the radii of the circular paths described by them.
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Q 112 Marks Questions2 Marks
A current I is flowing in an infinitely long conductor bent into the shape shown in Fig. If the radius of the curved part is R, find the magnetic field at the centre O. 
Image
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Q 122 Marks Questions2 Marks
Briefly explain Geiger-Marsden experiment. Show the variation of the number of particles scattered (N) with scattering angle $(\theta)$ in this experiment. What is the main conclusion that can be inferred from this plot?
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Q 142 Marks Questions2 Marks
$a.$ Show that the time period $(T)$ of oscillations of a freely suspended magnetic dipole of magnetic moment $(m)$ in a uniform magnetic field $(B)$ is given by $T=2 \pi \sqrt{\frac{I}{m B}}$, where $I$ is a moment of inertia of the magnetic dipole.
$b.$ Identify the following magnetic materials:
$i.$ A material having susceptibility $\left(\chi_m\right)=-0.00015$.
$ii.$ A material having susceptibility $\left(\chi_m\right)=10^{-5}$.
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Q 153 Marks Question3 Marks
A rectangular loop of wire $\text{ABCD}$ is kept close to an infinitely long wire carrying a current $I ( t )= l _0\left(1-\frac{t}{T}\right)$ for  $0 \leq t \leq T$ and $I (0)=0$ for $t > T ($Figure$)$. Find the total charge passing through a given point in the loop, in time $T$ . The resistance of the loop is $R$. 
Image
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Q 163 Marks Question3 Marks
$a.$ A toroidal solenoid with an air core has an average radius of $0.15 m$ , area of cross section $12 \times 10^{-4} m^2$ and $1200$ turns. Obtain the self inductance of the toroid. Ignore field variation across the cross section of the toroid.
$b.$ A second coil of $300$ turns is wound closely on the toroid above. If the current in the primary coil is increased from zero to $2.0 A$ in $0.05 s,$ obtain the induced emf in the secondary coil.
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Q 173 Marks Question3 Marks
Consider a two$-$slit interference arrangements $($Figure$)$ such that the distance of the screen from the slits is half the distance between the slits. Obtain the value of $D$ in terms of $\lambda$ such that the first minima on the screen fall at a distance $D$ from the center $O. $​​​​​​​
Image
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Q 183 Marks Question3 Marks
It is found experimentally that $13.6 eV$ energy is required to separate a hydrogen atom into a proton and an electron. Compute the orbital radius and the velocity of the electron in a hydrogen atom.
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Q 193 Marks Question3 Marks
Draw a plot showing the variation of binding energy per nucleon with mass number A. Write two important conclusions which you can draw from this plot. Explain with the help of this plot, the release in energy in the processes of nuclear fusion and fission.
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Q 205 Marks Questions5 Marks
$i.$ An ac source generating a voltage $V = V _0 \sin \omega t$ is connected to a capacitor of capacitance $C$ . Find the expression of the current I flowing through it. Plot a graph of $V$ and $I$ versus $\omega t$ to show that the current is $\frac{\pi}{2}$ ahead of the voltage.
$ii.$ A resistor of $200 \Omega$ and a capacitor of $15 \mu F$ are connected in series to a $220 V, 50 \ Hz$ ac source. Calculate the current in the circuit and the rms voltage across the resistor and the capacitor. Why the algebraic sum of these voltages is more than the source voltage?
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Q 215 Marks Questions5 Marks
$a$. Derive the expression for the current flowing in an ideal capacitor and its reactance when connected to an ac source of voltage $V = V _{ o } \sin \omega t$.
$b$. Draw its phasor diagram.
$c$. If resistance is added in series to capacitor what changes will occur in the current flowing in the circuit and phase angle between voltage and current.
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Q 225 Marks Questions5 Marks
Define the terms (i) capacitance of a capacitor (ii) dielectric strength of a dielectric. When a dielectric is inserted between the plates of a charged parallel plate capacitor, fully occupying the intervening region, how does the polarization of the dielectric medium affect the net electric field? For linear dielectrics, show that the introduction of a dielectric increases its capacitance by a factor $\kappa$, characteristic of the dielectric.
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Q 235 Marks Questions5 Marks
A capacitor of capacitance $C_1$ is charged to a potential $V_1$ while another capacitor of capacitance $C_2$ is charged to a potential difference $V_2$. The capacitors are now disconnected from their respective charging batteries and connected in parallel to each other.
$i.$ Find the total energy stored in the two capacitors before they are connected.
$ii.$ Find the total energy stored in the parallel combination of two capacitors.
$iii.$ Explain the reason for the difference of energy in parallel combination in comparison to the total energy before they are connected
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Q 245 Marks Questions5 Marks
You have learned in the text how Huygens’ principle leads to the laws of reflection and refraction. Use the same principle to deduce directly that a point object placed in front of a plane mirror produces a virtual image whose distance from the mirror is equal to the object distance from the mirror.
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Q 25Case study (4 Marks)4 Marks
Electric dipole consist of a pair of equal and opposite point charges separated by a small distance and its strength is measured by the dipole moment. The field around the dipole in which the electric effect of the dipole can be experienced is called the dipole field. 
Image
(i) The electric dipole moment is:
(a) a scalar quantity
(b) neither scalar nor vector quantity
(c) a vector quantity

(ii)Electric field due to the electric dipole is
(a) cylindrically symmetric (b) spherically symmetric (c) symmetric (d) asymmetric

(iii) The SI unit of dipole moment is:
(a) $C / m$ (b) C-m (c) $c / m ^2$ (d) $C - m ^2$

(iv) Charges $\pm 20 nC$ are separated by 5 mm . calculate the magnitude of dipole moment:-
(a) $10^{-7} C - m$ (b) $10^{10} C - m$ (c) $10^{-10} C - m$ (d) $10^{-8} C - m$

OR

When an electric dipole is placed in a uniform electric field, it experiences
(a) Neither any force nor any torque
(b) Force but no torque
(c) Force as well as torque
(d) Torque but no net force
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Q 26Case study (4 Marks)4 Marks
In an electromagnetic wave both the electric and magnetic fields are perpendicular to the direction of propagation, that is why electromagnetic waves are transverse in nature. Electromagnetic waves carry energy as they travel through space and this energy is shared equally by the electric and magnetic fields. Energy density of an electromagnetic waves is the energy in unit volume of the space through which the wave travels.
(i) The electromagnetic waves propagated perpendicular to both $\vec{E}$ and $\vec{B}$. The electromagnetic waves travel in the direction of
(a) $\vec{E} \cdot \vec{B}$
(b) $\vec{B} \cdot \vec{E}$
(c) $\vec{E} \times \vec{B}$
(d) $\vec{B} \times \vec{E}$

(ii) Fundamental particle in an electromagnetic wave is
(a) photon (b) phonon (c) electron (d) proton

(iii) Electromagnetic waves are transverse in nature is evident by
(a) diffraction (b) interference (c) polarisation (d) reflection

OR

The electric and magnetic fields of an electromagnetic waves are
(a) in opposite phase and parallel to each other
(b) in phase and parallel to each other.
(c) in phase and perpendicular to each other
(d) in opposite phase and perpendicular to each other

(iv) d) in opposite phase and perpendicular to each other
(a) frequency (b) wavelength (c) velocity (d) all these depend on each other
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