- The electric field (E) and electric potential (v) at a point inside a charged hollow metallic sphere are respectively (A) E=0 ,v=0 (B) E= 0 , v=v0 (a constant) (c) E# 0, V#0 ) (d) E= E0 (a constant ), v=0
- The dimensions of self-inductance are (A) MLT-2 A-2 (B) ML2T-1 A-1 (C) ML-1T-2A-2 (D) ML2T-2A-2
- In a circular loop of radius R , current I enters at point A and exists at point B as shown in figure . The value of the magnetic field at the centre o of the loop is
- The frequency of a photon of energy 1.326ev is (a) 1.18 * 10 14 HZ (b) 3.20 *10 14 HZ (c) 4.20 * 10 15 HZ (d) 4.80 * 10 15 Hz
- A metal ROD OF LENGTH 50CM IS HELD VERTICALLY AND MOVED WITH A VELOCITY OF 10m/s towards east . The horizontal component of the earth’s magnetic field at the place is 0.4G . the emf induced across the ends of the rod is : a) 0.1mv b) 0.2mv c) 0.8mv d) 1.6mv
- Germanium crystal is doped at room temp with a minute quantity of boron . the charge carriers in the doped semiconductor will be : a) electrons only b) holes only c) holes and few electrons d) electrons and few holes
- The effective resistance between points A and B in the given circuit is
- A capacitor and an inductor are connected in series across an ac source of voltage of variable frequency . The frequency is increased continuously . The nature of the circuit before and after the resonance will be a) inductive only b) capacitive only c) capacitive and inductive respectively d) inductive and capacitive respectively
- An alternating current is given by I = Io cos (100π)t . The least time the current takes to decrease from its maximum value to zero will be A) 1/200 s B) 1/150 s C) 1/100 s D) 1/50 s
- The mass number of two nuclei A and B are 27 and 64 respectively . The ratio of their radii (rA/rB ) will be : A) 27/64 B) 9/16 C) 3√3/8 D)3/4
- Isotones are the nuclides having : a) same mass numbers b) same atomic numbers c) same neutron number but different atomic number d) different neutron number and different mass number
- A p-n junction diode is forward biased . As a result (A) both the potential barrier height and the width of depletion layer decrease b) both the potential barrier height and width of depletion layer increase c) the potential barrier height decreases and the width of depletion layer increases d) the potential barrier height increases and the width of depletion layer decreases
- Assertion(A): A ray of light is incident normally on the face of a prism . The emergent ray will graze along the opposite face of the prism when the critical angle at glass –air interface is equals to the angle of prism . Reason (R) : The refractive index of a prism depends on angle of the prism
- Assertion(A) : A charged particle is moving with velocity v in x-y plane , making an angle φ (0<φ<π/2) with x-axis , if a uniform magnetic filed B is applied in the region along y axis the particle will move in a helical path with its axis parallel to x- axis . Reason (R): The direction of the magnetic force acting on a charged particle moving in a magnetic field is along the velocity of the particle .
- Assertion(A): The minimum negative potential applied to the applied to the anode in a photoelectric experiment at which photoelectric current becomes zero is called cut-off voltage Reason (R) : The threshold frequency for a metal is the minium frequency of incident radiation below which emission of photoelectrons does not takes place .
- Assertion (A) : EM waves do not require a medium for their propagation . Reason (R): EM waves are transverse waves .
- Two wires made of the same material have the same length (l) but different crossectional-area A1 and a2 . they are connected together with a cell of voltage v. find the ratio of the drift velocities of free electrons in the two wires when they are joined in (a)series and (b) parallel .
- Draw energy band diagrams of n-type and p-type semiconductors at temperature T>0 K . show the donor/acceptor energy levels with the order of difference of their energies from the bands.
- The ratio of the intensities at maxima to minima in YDSE is 25:9 . calculate the ratio of intensities of the interfering waves .
- (a) using the mirror equation and the formula of magnification ,deduce that “the virtual image produced by a convex mirror is always diminished in size and is located between the pole and the focus ” OR(b) A convex lens of focal length 10cm , a concave lens of focal length 15cm and a third lens of unknown focal length are placed coaxially in contact . if the focal length of the combination is 12cm ,find the nature and focal length of the third lens , if all lenses are thin . will the answer change if the lenses were thick ?
- Calculate the binding energy per nucleon (in Mev) of a helium nucleus (2He4) given m(2He4)= 4.002603u , mn=1.008665u, mH= 1.007825u
- Write the mathematical forms of three postulates of Bohr’s theory of the hydrogen atom . using them prove that for an electron revolving in the nth orbit , a) the radius of the orbit is proportional to n2 (b) the total energy of the atom is proportional to 1/n2
- A) Briefly explain Einstein”s photoelectric equation . B) Four metals with work function are listed below : K=2.3ev ,Na= 2.75ev ,Mo = 4.17ev ,Ni = 5.15ev . The radiation of wavelength 330nm of wavelength 330nm from a laser source placed 1m away falls on these metals . which of these metals will not show photoelectric emission ? what will happen if the laser source is brought closer to a distance of 50cm ?
- A) (i) write Biot-savart law in vector form . (ii) two identical circular coils a and b , each of radius R carrying currents I and √3I respectively,are placed concentrically in xy and yz plane respectively . find the magnitude and direction of the net magnetic field at their common centre . OR B) (i) A rectangular loop of sides l and b carries a current I clockwise . write the magnetic moment m of the loop and show its direction in a diagram .(ii) The loop is placed in a uniform magnetic field B and is free to rotate about an axis which is perpendicular to B. prove that the loop experiences no net force but a torque τ = m * B
- A) how are electromagnetic waves produced ? B) write the wavelength range and one of (i) microwaves (ii) ultraviolet waves
- A) Two concentric circular coil of radii r1 and r2 (r2 >> r1) are placed coaxially with their centre coinciding . if a current I is placed through the outer coil obtain the expression for mutual inductance of the arrangement . B) the current in a solenoid decreased steadily from 6mA to 2mA in 50ms . if an average emf of 0.4v is induced find the self inductance of the solenoid .
- Explain the process of formation of “depletion layer ” and “potential barrier” in a p-n junction region of a diode ,with the help of a suitable diagram . which feature of junction diode makes it suitable for its use as a rectifier ?
- Two point charges of -5μc and 2μc are located in free space at (-4cm ,0) and (6cm,0) respectively .a) calculate the amount of workdone to separate two charges at infinite distance . b)if this system of charges was initially kept in an electric field E=A/r2 , where A=8*104 N/cm2 , calculate bthe electrostatic potential energy of the system .
- When light travels from an optically denser medium to an optically rarer medium, at the interface it is partly reflected back into the same medium and partly refracted to the second medium. The angle of incidence corresponding to an angle of refraction 90° is called the critical angle (ic) for the given pair of media. This angle is related to the refractive index of medium 1 with respect to medium 2. Refraction of light through a prism involves refraction at two plane interfaces. A relation for the refractive index of the material of the prism can be obtained in terms of the refracting angle of the prism and the angle of minimum deviation. For a thin prism, this relation reduces to a simple equation. Laws of refraction are also valid for refraction of light at a spherical interface. When an object is placed in front of a spherical surface separating two media, its image is formed. A relation between object and image distance, in terms of refractive indices of two media and the radius of curvature of the spherical surface can be obtained. Using this relation for two surfaces of lens, ’lensemaker formula’ is obtained. A) A small bulb is placed at the bottom of a tank containing a transparent liquid (refractive index \( n \)) to a depth \( H \). The radius of the circular area of the surface of liquid, through which the light from the bulb can emerge out, is \( R \). Then \( \left( \frac{R}{H} \right) \) is: B) A parallel beam of light is incident on a face of a prism with refracting angle 60°. The angle of minimum deviation is found to be 30°. The refractive index of the material of the prism is close to: c) The angle of minimum deviation for a ray of light incident on a thin prism, made of crown glass (\( n = 1.52 \)) is \( \delta_m \). If the prism was made of dense flint glass (\( n = 1.62 \)) instead of crown glass, the angle of minimum deviation will: d) An object is placed in front of a convex spherical glass surface (n=1.5n=1.5 and radius of curvature RR) at a distance of 4R4R from it. As the object is moved slowly close to the surface, the image formed is: e) A double-convex lens, made of glass of refractive index 1.5, has focal length 10 cm. The radius of curvature of its each face, is:
- In a metallic conductor, an electron, moving due to thermal motion, suffers collisions with the heavy fixed ions but after collision, it will emerge out with the same speed but in random directions. If we consider all the electrons, their average velocity will be zero. When an electric field is applied, electrons move with an average velocity, known as drift velocity (va). The average time between successive collisions is known as relaxation time (t). The magnitude of drift velocity per unit electric field is called mobility (u). An expression for current through the conductor can be obtained in terms of drift velocity, number of electrons per unit volume (n), electronic charge (-e), and the cross-sectional area (A) of the conductor. This expression leads to an expression between current density (ĵ) and the electric field (E). Hence, an expression for resistivity (p) of a metal is obtained. This expression helps us to understand increase in resistivity of a metal with increase in its temperature, in terms of change in the relaxation time (t) and change in the number density of electrons (n). -> (i) Consider two cylindrical conductors A and B, made of the same metal connected in series to a battery. The length and the radius of B are twice that of A. If μд and μg are the mobility of electrons in A and B respectively, then “A is: (A) 12 2 (C) 2 HB (B) 4 (D) 1 (ii) A wire of length 0.5 m and cross-sectional area 1-0 × 10-7 m² is connected to a battery of 2 V that maintains a current of 1-5 A in it. The conductivity of the material of the wire (in Q-1 m-1) is: (A) 2.5 × 104 1 1 (B) 3.0 x 105 (C) 3.75 × 106 (D) 5.0 × 107 55/7/2
- A) (i) explthe with the help of labeled ray diagram the formation of final image by an astronomical telescope at infinity . write the expression for its magnifying power .(ii)the total magnification produced by a compound microscope is 20 . The magnification produced by the eye piece is 5 . when the microscope is focused on a certain object , the distance between the objective and eye piece is observed to be 14cm . calculate the focal length of the objective and eye piece given that the least distance of didtinct vision is 25cm . OR B)(i) Two coherent light waves each of intensity Io superpose each other and produce interference patteren on a screen . obtain the expression for the resulatant intensity at a point where the phase difference between the waves is φ , write its maximum and minimum possible values . (ii) In a single slit diffraction experiment the aperature of the slit is 3mm and the separation between the slit and the screen is 1.5 m . A monochromatic light of wavelength 600nm is normally incident on the slit . calculate the distance of (I) first order minimum and (II) second order maximum from the centre of the screen .
- (a)(i)A parallel plate capacitor with plate area QA and plate separation A has a capacitance C0 . A slab of dielectric constant K having area A and thickness (d/4 ) is inserted in the capacitor , parallel to the plates . Find the new value of its capacitance . (ii) you are provide with a large number of 1μF identical capacitors and a power supply of 1200 v . The dielectric medium used in each capacitor can withstand up to 200v only . Find the minimum number of capacitor and their arrangement required to build a capacitor system of equivalent capacitance 2μF for use with this supply . OR b) (i) An electric dipole of dipole moment p consists of point charges q and –q separated by 2a . derive an expression for electric potential in terms of its dipole moment at a point at a distance (x>>a) from its centre and lying (I) along its axis and (II) along its bisector line . (ii) An electric dipole of moment P= (0.8 Î+ 0.6Ĵ) 10 -29 cm is placed in an electric field E= 1* 10 7 κ v/m . calculate the magnitude of the torque acting on it and the angle it makes with the x-axis at this instant .
- A)(i) with the help of a labeled diagram , explain the principle of working of a moving coil galvanometer . Write the purpose of using (i) radial magnetic field (ii) soft iron core in it
(ii) Define current sensitivity of a Galvanometer . “increasing the current sensitivity may not necessarily increase the voltage sensitivity ” . Give reason