Physics Outside Delhi Set 1 2022-2023 Science (English Medium) Class 12 Question Paper Solution

The magnitude of the electric field due to a point charge object at a distance of 4.0 m is 9 N/C. From the same charged object the electric field of magnitude, 16 N/C will be at a distance of ______.

1 m

2 m

3 m

6 m

A point P lies at a distance x from the midpoint of an electric dipole on its axis. The electric potential at point P is proportional to ______.

`1/x^2`

`1/x^3`

`1/x^4`

`1/x^{1"/"2}`

A current of 0.8 A flows in a conductor of 40 Ω for 1 minute. The heat produced in the conductor will be ______.

1445 J

1536 J

1569 J

1640 J

A cell of emf E is connected across an external resistance R. When current 'I' is drawn from the cell, the potential difference across the electrodes of the cell drops to V. The internal resistance 'r' of the cell is ______.

`((E - V)/E)R`

`((E - V)/R)`

`((E - V)R)/I`

`((E - V)/V)R`

Beams of electrons and protons move parallel to each other in the same direction. They ______.

attract each other.

repel each other.

neither attract nor repel.

the force of attraction or repulsion depends upon the speed of the beams.

A long straight wire of radius 'a' carries a steady current 'I'. The current is uniformly distributed across its area of cross-section. The ratio of the magnitude of magnetic field `vecB_1` at `a/2` and `vecB_2` at distance 2a is ______.

`1/2`

1

2

4

If `vecE` and `vecB` represent electric and magnetic field vectors of the electromagnetic wave, the direction of propagation of the electromagnetic wave is along ______.

`vecE`

`vecB`

`vec(B) × vec(E)`

`vecE × vecB`

A ray of monochromatic light propagating in the air is incident on the surface of the water. Which of the following will be the same for the reflected and refracted rays?

Energy carried

Speed

Frequency

Wavelength

A beam of light travels from air into a medium. Its speed and wavelength in the medium are 1.5 × 10⁸ ms^-1 and 230 nm respectively. The wavelength of light in the air will be ______.

230 nm

345 nm

460 nm

690 nm

Which one of the following metals does not exhibit emission of electrons from its surface when irradiated by visible light?

Rubidium

Sodium

Cadmium

Caesium

A hydrogen atom makes a transition from n = 5 to n = 1 orbit. The wavelength of photon emitted is λ. The wavelength of photon emitted when it makes a transition from n = 5 to n = 2 orbit is ______.

`8/7lambda`

`16/7lambda`

`24/7lambda`

`32/7lambda`

The curve of binding energy per nucleon as a function of atomic mass number has a sharp peak for helium nucleus. This implies that helium nucleus is ______.

radioactive

unstable

easily fissionable

more stable nucleus than its neighbours

In an extrinsic semiconductor, the number density of holes is 4 × 10²⁰ m^-3. If the number density of intrinsic carriers is 1.2 × 10¹⁵ m^-3, the number density of electrons in it is ______.

1.8 × 10⁹ m^-3

2.4 × 10¹⁰ m^-3

3.6 × 10⁹ m^-3

3.2 × 10¹⁰ m^-3

Pieces of copper and of silicon are initially at room temperature. Both are heated to temperature T. The conductivity of ______.

both increases.

both decreases.

copper increases and silicon decreases.

copper decreases and silicon increases.

The formation of the depletion region in a p-n junction diode is due to ______.

movement of dopant atoms

diffusion of both electrons and holes

drift of electrons only

the drift of holes only

• Assertion (A): Diamagnetic substances exhibit magnetism.
• Reason (R): Diamagnetic materials do not have a permanent magnetic dipole moment.

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Both Assertion (A) and Reason (R) are true and Reason (R) is NOT the correct explanation of Assertion (A).

Assertion (A) is true and Reason (R) is false.

Assertion (A) is false and Reason (R) is also false.

• Assertion (A): Work done in moving a charge around a closed path, in an electric field is always zero.
• Reason (R): Electrostatic force is a conservative force.

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Both Assertion (A) and Reason (R) are true and Reason (R) is NOT the correct explanation of Assertion (A).

Assertion (A) is true and Reason (R) is false.

Assertion (A) is false and Reason (R) is also false.

• Assertion (A): In Young's double slit experiment all fringes are of equal width.
• Reason (R): The fringe width depends upon the wavelength of light (λ) used, the distance of the screen from the plane of slits (D) and slits separation (d).

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Both Assertion (A) and Reason (R) are true and Reason (R) is NOT the correct explanation of Assertion (A).

Assertion (A) is true and Reason (R) is false.

Assertion (A) is false and Reason (R) is also false.

State how a moving coil galvanometer can be converted into an ammeter.

How are infrared waves produced?

Why are infra-red waves often called heat waves? Explain.

Give any two uses of infrared waves.

How are X-rays produced?

Write two uses of the following radiation.

X-rays

In the given figure the radius of curvature of the curved face in the planoconvex and the planoconcave lens is 15 cm each. The refractive index of the material of the lenses is 1.5. Find the final position of the image formed.

What happens to the interference pattern when two coherent sources are infinitely close?

What happens to the interference pattern when two coherent sources are far apart from each other?

What is meant by ionisation energy?

Write the ionisation energy value for the hydrogen atom.

What is mass defect?

How mass defect is related to the stability of the nucleus?

Draw an energy band diagram for a p-type semiconductor at T > 0 K.

Answer the following giving reasons:

A p-n junction diode is damaged by a strong current.

Answer the following giving reasons:

Impurities are added to intrinsic semiconductors.

Two charged conducting spheres of radii a and b are connected to each other by a wire. Find the ratio of the electric fields at their surfaces.

A parallel plate capacitor (A) of capacitance C is charged by a battery to voltage V. The battery is disconnected and an uncharged capacitor (B) of capacitance 2C is connected across A. Find the ratio of final charges on A and B.

A parallel plate capacitor (A) of capacitance C is charged by a battery to voltage V. The battery is disconnected and an uncharged capacitor (B) of capacitance 2C is connected across A. Find the ratio of total electrostatic energy stored in A and B finally and that stored in A initially.

Define Current density.

Define relaxation time.

Derive an expression for resistivity of a conductor in terms of the number density of charge carriers in the conductor and relaxation time.

A series CR circuit with R = 200 Ω and C = (50/π) µF is connected across an ac source of peak voltage ε₀ = 100 V and frequency v = 50 Hz. Calculate (a) impedance of the circuit (Z), (b) phase angle (Φ), and (c) voltage across the resistor.

Define the critical angle for a given pair of media and total internal reflection. Obtain the relation between the critical angle and refractive index of the medium.

Distinguish between nuclear fission and fusion giving an example of each.

Explain the release of energy in nuclear fission and fusion on the basis of binding energy per nucleon curve.

How is the size of a nucleus found experimentally? Write the relation between the radius and mass number of a nucleus.

Answer the following question.

Show that the density of the nucleus is independent of its mass number A.

Use Gauss' law to derive the expression for the electric field `(vecE)` due to a straight uniformly charged infinite line of charge density λ C/m.

An infinitely long positively charged straight wire has a linear charge density λ. An electron is revolving in a circle with a constant speed v such that the wire passes through the centre, and is perpendicular to the plane, of the circle. Find the kinetic energy of the electron in terms of the magnitudes of its charge and linear charge density λ on the wire.

Draw a graph of kinetic energy as a function of linear charge density λ.

Consider two identical point charges located at points (0, 0) and (a, 0).

Is there a point on the line joining them at which the electric field is zero?

Consider two identical point charges located at points (0, 0) and (a, 0).

Is there a point on the line joining them at which the electric potential is zero?

Justify your answers for each case.

State the significance of the negative value of electrostatic potential energy of a system of charges.

Three charges are placed at the corners of an equilateral triangle ABC of side 2.0 m as shown in the figure. Calculate the electric potential energy of the system of three charges.

Define the coefficient of self-induction.

Derive the expression for the self-inductance of a long solenoid of cross sectional area A and length l, having n turns per unit length.

Calculate the self-inductance of a coil using the following data obtained when an AC source of frequency `(200/pi)` Hz and a DC source are applied across the coil.

With the help of a labelled diagram, describe the principle and working of an ac generator. Hence, obtain an expression for the instantaneous value of the emf generated.

The coil of an ac generator consists of 100 turns of wire, each of area 0.5 m². The resistance of the wire is 100 Ω. The coil is rotating in a magnetic field of 0.8 T perpendicular to its axis of rotation, at a constant angular speed of 60 radians per second. Calculate the maximum emf generated and power dissipated in the coil.

State Huygen's principle.

With the help of a diagram, show how a plane wave is reflected from a surface. Hence verify the law of reflection.

A concave mirror of focal length 12 cm forms three times the magnified virtual image of an object. Find the distance of the object from the mirror.

Draw a labelled ray diagram showing the image formation by a refracting telescope. Define its magnifying power.

Write two important limitations of a refracting telescope over a reflecting-type telescope.

The focal lengths of the objective and the eye-piece of a compound microscope are 1.0 cm and 2.5 cm respectively. Find the tube length of the microscope for obtaining a magnification of 300.

Read the following paragraph and answer the questions.

1. Explain the reason for the jumping of the ring when the switch is closed in the circuit.
2. What will happen if the terminals of the battery are reversed and the switch is closed? Explain.
3. Explain the two laws that help us understand this phenomenon.

Briefly explain various ways to increase the strength of the magnetic field produced by a given solenoid.

Read the following paragraph and answer the questions.

1. Which light beam has the highest frequency and why?
2. Which light beam has the longest wavelength and why?
3. Which light beam ejects photoelectrons with maximum momentum and why?

What is the effect of threshold frequency and stopping potential on increasing the frequency of the incident beam of light? Justify your answer.