- The plates p1 and p2 of a 2μF capacitor are at potential 25 v and -25 v respectively . The charge on plate p1 will be a)0.02mc b)0.1mc c)0.1 μc d) 1 μc
- A proton is taken from point p1 to point p2 both located in an electric field . The potentials at point p1 and p2 are -5v and +5v respectively . Assuming that kinetic energies of the proton at points p1 and p2 are zero , the work done on the proton is : a) -1.6 * 10 -18 j b) 1.6 * 10 -18 J c) zero d) 0.8 * 10 -18 j
- A 2cm segment of wire carrying 5A current in positive y direction lies along y axis as shown in figure . The magnetic field at a point (3m,4m,0) due to this segment (part of this circuit ) is : a)0.12nT Ĵ b) –(0.10nT)Ĵ c) –(0.24nT) k^
- Which of the following is dia magnetic substance a)gadolinium b)sodium c) copper chloride d) sodium chloride
- A current carrying circular loop of magnetic moment M is suspended in a vertical plane in an external magnetic field B such that its plane is normal to B . The workdone in rotating this loop by 45° about an axis perpendicular to B is closest to a) -0.3 MB b) 0.3 MB c) -1.7 MB d) 1.7MB
- The average value of the alternating voltage v=157 sin wt over its first half-cycle is : a) 157 v b) 157/√2 v c) 78.5 v d) 100 v
- Consider a solenoid of length l and area of cross-section A with fixed number of turns . The self inductance of the solenoid will increase if : A) both l and A are increased B) l is decreased and A is increased C ) l is increased and A is decreased D) both l and A are decreased
- A plane electromagnetic wave is travelling in air in x direction . At a particular moment its electric field E is along Y direction , at that moment the magnetic field B is along a) +z direction and in phase with E b) –Z direction and in phase with E c) +z direction and out of phase with E d) –Z direction and out of phase with E
- A proton and an alpha particle having equal velocities approach a target nucleus . They come momentarily to rest and then reverse their directions. The ratio of distance of closest approach of the proton to that of the alpha particle will be : a) ½ b) 2 c) ¼ d) 4
- The wavelength of matter wave associated with an electron of kinetic energy K is ƛ . if the kinetic energy of the electron is doubled the associated wavelength becomes A) ƛ/√2 B) ƛ/2 C)√2 ƛ D) 2ƛ
- An electron makes a transition from n=2 level to n=1 level in the Bohr model of Hydrogen atom . its period of revolution : a) increases by 87.5% b) decreases by 87.5% c) increases by 43.75 % d) decreases by 43.75%
- Si is doped with a pentavalent element . The energy required to set the additional electron free is about : a) 0.01ev b) 0.05ev c) 0.72ev d) 1.1ev
- Assertion (A) : In a semiconductor the electrons in the conduction band have lesser energy than those in the valence band . Reason (R) : Donor energy level is just above the valence band in a semiconductor .
- Assertion (A): photoelectric effect demonostrates the particle nature of light . Reason (R) : photoelectric current is proportional to frequency of incident radiation .
- Assertion : A proton and an electron enter a uniform magnetic field B with the same momentum P such that p is perpendicular to B . they describe circular path of the same radius . reason (R) : in a magnetic field orbital radius r is equal to p/qB .
- Assertion (A) : A convex lens when immersed in a liquid disappears . reason (R) : The refractive indices of material of the lens and the liquid are equal .
- A) what is meant by “relaxation time ” of free electrons in a conductor ? show that the resistance of a conductor can be expressed by R = ml/ne2τA , where symbols have their usual meanings . OR B) Draw the circuit diagram of a wheat stone bridge , obtain the condition when no current flows through the galvanometer in it .
- The magnifying power of an astronomical is 24 . In normal adjustment distance between its two lenses is 150 cm . find the focal length of the objective lens ?
- What is a sustained or stable interference pattern? what are the conditions for obtaining such an interference pattern ?
- Light of wavelength 600nm is incident on potassium (work function 2.3ev) . will photoelectric emission of electrons occurs ? what is the longest wavelength that will cause photoemission of electrons ? (taken hc= 1240ev.nm)
- suppose a pure si crystal has 5* 10 28 atoms m-3 . it is doped by 1ppm concentration of boron . calculate the concentration of holes and electrons given that ni = 1.5 * 10 16 m -3 . is the doped crystal n-type or p-type ?
- A current of 1.6A flows through a wire when a potential difference of 1v is applied across it . The length and cross-sectional area of the wire are 1m and 1*10 -7 m2 respectively . calculate a) electric field across the wire b) current density c) average relation time (τ) (Number density of free electrons in the wire is 9 *10 28 m-3 )
- An electron (charge –e , mass m ) is revolving around a nucleus , in a hydrogen atom in a circle of radius r . derive an expression in vector form for the magnetic dipole moment μe in term of its orbital angular momentum L . what is gyromagnetic ratio?
- Prove that induced charge depends on the net charge in the magnetic flux and not on the time interval of the flux change?
- The electric fields in an emw in vaccum is given by E= 6.3N/C { cos (1.5rad/m)y + (4.5*10 8rad/sec)t} Î a)find wavelength and frequency of wave b)what is the amplitude of magnetic field c) write expression for magnetic field of the wave ?
- State Bohr’s second postulate for his theory of Hydrogen atom . Prove that the radius of Bohr’s orbit of a hydrogen atom is directly proportional to n2 , where n is the principal quantum number ?
- A) Define atomic mass unit (u) . B) Calculate the energy required to separate a deuteron into its constituent parts (a proton and a neutron ) , given : m(D)= 2.014102u , mH = 1.007825u, mn= 1.008665u
- A) Draw the circuit diagrams for obtaining the V-I characteristics of a p-n junction diode ? Explain briefly the salient features of the v-I characteristics in (a) forward biasing (b) reverse biasing or B) on the basis of energy band diagram distinguish between a) an insulator b) a semiconductor c) a conductor
- The figure shows four pairs of parallel identical conducting plates, separated by the same distance 2.0 cm and arranged perpendicular to x-axis. The electric potential of each plate is mentioned. The electric field between a pair of plates is uniform and normal to the plates. A) For which pair of the plates is the electric field E along i? (A) I (B) II (C) III (D) IV B)An electron is released midway between the plates of pair IV. It will: (A) move along î at constant speed (B) move along -î at constant speed (C) accelerate along î (D) accelerate along –î C) Let Vo be the potential at the left plate of any set, taken to be at x = 0 m. D) Then potential V at any point (0 ≤ x ≤2 cm) between the plates of that set can be expressed as: (A) V = Vo + ax (B) V = Vo + ax² (C) V = Vo + ax^(1/2) (D) V = Vo + a x^(3/2) where a is a constant, positive or negative. E)Let E1, E2, E3 and E4 be the magnitudes of the electric field between the pairs of plates, I, II, III and IV respectively. Then: (A) E1 > E2 > E3 > E4 (B) E3 > E4 > E1 > E2 (C) E4 > E3 > E2 > E1 (D) E2 > E3 > E4 > E1 OR An electron is projected from the right plate of set I directly towards its left plate. It just comes to rest at the plate. The speed with which it was projected is about: (Take (e/m) =1.76 x10¹¹ C/kg) (A) 1.3 x10^5 m/s (B) 2.6 x10^6 m/s (C) 6.5 x10^5 m/s (D) 5.2 x 10^7 m/s
- Diffraction and interference are closely related phenomena that occur together. Diffraction is the phenomenon of bending of light around the edges of the obstacle, while interference is the combination of waves that results in a new wave pattern. In order to get interference, there must be at least two waves that are diffracting. So while diffraction can occur without interference, interference cannot occur without diffraction. Two slits of width 2 µm each in an opaque material are separated by a distance of 6 µm. Monochromatic light of wavelength 450 nm is incident normally on the slits. One finds a combined interference and diffraction pattern on the screen. (i) The number of peaks of the interference fringes formed within the central peak of the envelope of the diffraction pattern will be: (a) 2 (b) 3 (c) 4 (d) 6 (ii) The number of peaks of the interference formed if the slit width is doubled while keeping the distance between the slits same will be: (a) 1 (b) 2 (c) 3 (d) 4 (iii) Consider the diffraction of light by a single slit described in this case study. The first minimum falls at an angle θ equal to: (a) Sin⁻¹ (0.12) (b) Sin⁻¹ (0.225) (c) Sin⁻¹ (0.32) (d) Sin⁻¹ (0.45) (iv) The number of bright fringes formed due to interference on 1 m of screen placed at 4/3 m away from the slits is: (a) 2 (b) 3 (c) 6 (d) 10
- A)(i) obtain the expression for the capacitance of parallel plate capacitor with a dielectric medium between its plates . (ii)A charge of 6μc is given to a hollow metallic sphere of radius 0.2 m . Find the potential at (i)the surface (ii) the centre of the sphere .
OR
(b) (i) A charge +Q is placed on a thin conducting spherical shell of radius R . Use Gauss’s theorem to derive an expression for the electric field at a point lying (i) inside (ii) outside the shell .
(ii) Show that the electric field for same charge density (σ) is twice in case of a conducting plate or surface than in a non-conducting sheet ?
- (a)(i) (1) what is meant by current sensitivity of a Galvanometer ? Mention the factors on which it depends ?
(2) A galvanometer of resistance G is converted into a voltmeter of range (0-v) by using a resistance R . Find the resistance in terms of R and G required to convert it into a voltmeter of range (0-v/2).
(ii) The magnetic flux through a coil of resistance 5Ω increases with time as φ = (2t3 + 5t2+6t)mwb . Find the magnitude of induced current through the coil at t= 2 s .
Or b(i) A rectangular coil of N turns and area of cross-section A is rotated at a steady angular speed ω in a uniform magnetic field . Obtain an expression for the emf induced in the coil at any instant of time .
(ii)Two coplanar and concentric circular loops L1 and L2 are placed co-axially with their centres coinciding. The radii of L1 and L2 are 1cm and 100cm respectively . calculate the mutual inductance of the loop .(take π2=10)
- (a)(i) Trace the path of a ray of light showing refraction through a triangular prism and hence obtain an expression for angle of deviation (δ) in terms of A ,i and e ,where symbols have their usual meanings . Draw a graph showing the variation of angle of deviation with angle of incidence .
(ii) in the figure , a ray of light is incident on a transparent liquid contained in a thin glass box at an angle of 45° with its one face . The emergent ray passes along the face AB . find the refractive index of liquid .
b)(i) The displacement of two light waves , each of amplitude a and frequency ω emanating from two coherent sources of light are given by y1 = a cos wt and y2= a cos (wt +φ) , φ is the phase difference between the two waves . These light waves superpose at a point . obtain the expression for the resultant intensity at that point . (ii) In Young’s double slit experiment find the ratio of intensities at two points on a screen when waves emanating from two slis reaching these points have path difference (i) ƛ/6 (ii) ƛ/12 .