The SI unit of electric field intensity is 

1

(a)

N

(b)

N/C

(c)

C/m²

(d)

N/m²

Which of the following is not an insulator?

1

(a)

glass

(b)

rubber

(c)

ebonite

(d)

human body

A current carrying circular loop of radius R is placed in the x-y plane with centre at the origin. Half of the loop with x>0 is now bent so that it now lies in the y-z plane.

1

(a)

The magnitude of magnetic moment now diminishes

(b)

The magnetic moment does not change 

(c)

The magnitude of \(\overset { \rightarrow }{ B } \) at (0,0,z), z>>R increases.

(d)

The magnitude \(\overset { \rightarrow }{ B } \) at (0,0,z), z>>R is unchanged.

A magnetic needle suspended parallel to a magnetic field requires \(\sqrt { 3 } J\) of work to turn it through \({ 60 }^{ ° }.\) The torque needed to maintain the needle in this position will be :

1

(a)

\(2\sqrt { 3 } J\)

(b)

\(3J\)

(c)

\(\sqrt { 3 } J\)

(d)

\(\frac { 3 }{ 2 } J\)

For an LCR circuit, the power transferred from the driving source to the driven oscillator from the driving source tothe driven oscillator is P = I²Z cos \(\phi \).

1

(a)

Here, the power factor cos \(\phi \ge 0,\ P\ge 0\)

(b)

The driving force can given no energy to the oscillator (P = 0) in some cases

(c)

The driving force can not syphon out (P<0) the energy out of oscillator

(d)

The driving force can take away energy out of the oscillator

A red LED emits light of 0.1 watts uniformly around it. The amplitude of the electric field of the light at a distance of 1 m from the diode is 

1

(a)

1.73 V/m

(b)

2.45 V/m

(c)

5.48 V/m

(d)

7.75 V/m

The correct formula for magnifying power of a simple microscope is

1

(a)

\(m=\left( 1+\frac { f }{ d } \right) \)

(b)

\(m=\left( 1-\frac { d }{ f } \right) \)

(c)

\(m=\left( 1+\frac { d }{ f } \right) \)

(d)

\(m=\left( 1-\frac { f }{ d } \right) \)

Electrons used in an electron microscope are accelerated by a voltage of 25kV. If the voltage is increased to 100 kV then the de-Broglie wavelength associated with the electrons would

1

(a)

increase by 2 times

(b)

decrease by 2 times

(c)

decrease by 4 times

(d)

increase by 4 times

Taking the Bohr radius as a₀ = 53pm, the radius of Li⁺⁺ ion its ground state, on the basis of Boh''s model, will be about

1

(a)

53pm

(b)

27pm

(c)

18pm

(d)

13pm

In a semiconducting material (1/5) th of the total current is carried by the holes and the remaining is carried by the holes and the remaining is carried by the electrons. The drift speed of electrons is twice that of holes at this temperature The ratio between the number densities of electrons and holes is

1

(a)

21/6

(b)

5

(c)

3/8

(d)

2

A beam of light is incident on a glass slab in a direction as shown in the figure. The reflected light is analysed by a polaroid prism. On rotating the polaroid,

1

(a)

the intensity remains unchanged

(b)

the intensity is reduced to zero and remains at zero

(c)

the intensity gradually reduced to zero and then again increases

(d)

the intensity increase continuously

(e)

the intensity increases initially and remains constant afterwards

Name the physical quantity which has its unit joule \({ coulomb }^{ -1 }\\ \)

1

(a)

Electric potential.

Electric flux over an area in an electric field represents the ................ crossing this area.

1

(a)

total number of electric lines of force

The Sequence of bands marked on a carbon resistor are: Red, Red, Red, Silver, Write the value of resistance with tolerance.

1

(a)

22*10^{2 _{\(\Omega \)}} \(\pm\) 10%

Total resistance of the circuit is R/3 in which three identical resistors are connected in parallel. Find the value of each resistance?

1

(a)

R

Does an electric charge moving along the direction of magnetic field experiences a force experiences a force?

1

(a)

Metallic wire 1m in length is moving normally across a field of 0.1 T with a speed of 5 \(m{ s }^{ -1 }\). Find the e.m.f. between the ends of the wire.

1

(a)

Induced e.m.f. \(e=Bl\upsilon =0.1\times 1\times 5=0.5V\)

What is common between different types of e.m. radiations?

1

(a)

1. Why must both the objective and the eye-piece of a compound microscope have short focal lengths ?

   1

   (a)

2. The de-Broglie wavelength associated with an electron accelerated through a potential difference V is \(\lambda .\) What will be wavelength when accelerating potential is increased to 4 V?

   1

   (a)

   In first case.

                       \(\lambda =\frac { h }{ \sqrt { 2meV } } \)

   In Second case

                        \(\lambda '=\frac { h }{ \sqrt { 2me(4V) } } \)

   \(\therefore \)                 \(\frac { \lambda ' }{ \lambda } =2or\lambda '=2\lambda \)​​​​​​​

    

1. If a semiconductor has an intrinsic carrier concentration of 1.04 x 10¹⁴ /m³ when doped with 10^28/m³ phosphorous atoms, calculate the concentration of hole /m³ at room temperature.

   1

   (a)

2. Draw a block diagram of a generalized communication system.

   1

   (a)

   
   Alternatively: Also accept if the student gives only the following diagram:
   

A 800pF capacitor is charged by a 100V battery. After sometime the battery is disconnected. The capacitor is then connected to another 800pF capacitror. What is the electrostatic energy stored?

2

(a)

A wire of resistance \(1\Omega \) is stretched to double its length. What is the new resistance?

2

(a)

Write the expression for Lorentz magnetic force on a particle of charge 'q' moving with velocity \(^{\rightarrow}_{V}\) in a magnetic field \(^{\rightarrow}_{B}\).  Show that no work is done by this force on the charged particle.

2

(a)

A e.m. wave, Y₁, has a wavelength of 1cm while another e.m. wave, Y₂, has a frequency of 10¹⁵ Hz. Name these two types of waves and write one useful application for each.

2

(a)

1. A prism can produce a spectrum of white light but a glass slab having the same material as a prism cannot produce any spectrum. why?

   2

   (a)

2. A message signal of frequency 10 kHz and peak voltage 10 V is used to modulate a carrier wave of frequency 1 MHz and peak voltage 20 V. Determine
   (i) The modulation index
   (ii) the side bands produced.

   2

   (a)

1. A ray of light passes through an equilateral glass prism, such that the angle of incidence is equal to the angle of emergence. If the angle of emergence is ¾ times the angle of the prism, Calculate the refractive index of the glass prism

   2

   (a)

A two point charges q₁ and q₂ of magnitude 10^-7 C and - 10^-7 C, respectively are placed 0.2 m apart. Calculate the electric fields at points A, B and C as shown in the figure.
     

3

(a)

A resistance of 900 \(\Omega \) is connected in series with a galvanometer of resistance 100 \(\Omega \)  . A potential difference of 1 volt produces 100 division deflection in the galvanomter. Find the figure of merit of galvanometer.

3

(a)

If the effective current in a 50 cycle a.c. circuit is 5 A, what is the peak value of current? What is the current 1/600 sec. after it was zero?

3

(a)

Answer the following questions.
(i) Name the electromagnetic waves which are used for the treatment  of certain forms of cancer. Write their frequency range.
(ii) Thin ozone layer on top of stratosphere is crucial for human survival. Why?
(iii) Why is the amount of the momentum transferred by the electromagnetic waves incident on the surface so small?

3

(a)

What is meant by selectivity and sensitivity of radio receiver?

3

(a)

An object is placed at (i) 10 cm, (ii) 5 cm in front of a concave mirror of radius of curvature 15 cm. Find the position, nature, and magnification of the image in each case.

3

(a)

(a) A point object is placed in front of a double convex lens (of refractive index n =n₂/n₁ with respect air) with its spherical faces of radii of curvature R₁ and R_2.. Show the path of rays due to surface to obtain the formation of the real image of the object.
Hence obtain the lens maker's formula for a thin lens.
(b) A double convex lens having both faces of the same radius of curvature has refractive index 1.55. Find out the radius of curvature of the lens required to get the focal length of 20 cm.

3

(a)

Draw the "Energy bands', diagrams for a(i) pure semiconductor, (ii) insulator. How does the energy band, for a pure semiconductor, get affected when this semiconductor is doped with (a) an acceptor impurity (b) donor impurity?
Hence discuss why the 'holes, and the 'electrons' respectively, become the 'majority charge carriers' in these two cases?
Write the two process involved in the formation of p-n junction.

5

(a)

What is meant by (i) half life and (ii) average life of a radioactive substance? Derive expression for them. What is relation between average life and half life.

5

(a)

What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20 cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.

5

(a)

A dipole consisting of an electron and a proton separated by a distance of \(4\times 10^{-10}m\) is situated in an electric field of intensity \(3\times 10^5NC^{-1}\) at an angle of 30^o with the field. Calculate the dipole moment and the torque acting on it. Charge e on an electron = \(1.6\times 10^{-19}C\)

5

(a)

Find the de-Broglie wavelength(in \(\overset { \circ }{ A } \) ) associated with an example with an electron moving with a velocity 0.6c, where c=\(3\times { 10 }^{ 8 }m/s\)and rest mass of electron=\(9.1\times { 10 }^{ -31 }kg\), \(h=6.6\times { 10 }^{ -34 }Js\)

5

(a)