47. Two ideal diodes are connected to a battery as shown in the circuit. The current supplied by the battery is :

47. Two ideal diodes are connected to a battery as shown in the circuit. The current supplied by the battery is :

46. C and Si both have same lattice structure, having 4 bonding electrons in each. However, C is insulator whereas Si is intrinsic semiconductor. This is because :

46. C and Si both have same lattice structure, having 4 bonding electrons in each. However, C is insulator whereas Si is intrinsic semiconductor. This is because :

(a) In case of C the valence band is not completely filled at absolute zero temperature.

(b) In case of C the conduction band is partly filled even at absolute zero temperature.

(c) The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si they lie in the third.

(d) The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit.

Answer :  (c) The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si they lie in the third.

71. The magnifying power of a telescope is 9 . When it is adjusted for parallel rays the distance between the objective and eyepiece is 20 cm. The focal length of lenses are :

57. A ray of light is incident at an angle of incidence, i, on one face of prism of angle A (assumed to be small) and emerges normally from the opposite face. If the refractive index of the prism is μ, the angle of incidence i, is nearly equal to :

56. For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index ?

46. When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have refractive index is ___ ?

45. A concave mirror of focal length ’ $f_1$ ’ is placed at a distance of ’ d ’ from a convex lens of focal length ’ $f_2$ ’. A beam of light coming from infinity and falling on this convex lens-concave mirror combination returns to infinity. The distance ’ d ’ must equal :

4. A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its end closer to the pole is 20 cm away from the mirror. The length of the image is ?

A parallel plate capacitor has a uniform electric field E in the space between the plates. If the distance between the plates is d and area of each plate is A, the energy stored in the capacitor is ?

The potential energy of particle in a force field is U = A / r^2 − B / r , where A and B are positive constants and r is the distance of particle from the centre of the field. For stable equilibrium, the distance of the particle is ?

Four point charges −Q, −q, 2q and 2Q are placed, one at each corner of the square. The relation between Q and q for which the potential at the centre of the square is zero is ?

What is the flux through a cube of side ’ a ’ if a point charge of q is at one of its corner ?

An electric dipole of moment p ′ is placed in an electric field of intensity ’ E ’. The dipole acquires a position such that the axis of the dipole makes an angle θ with the direction of the field. Assuming that the potential energy of the dipole to be zero when = 90◦ , the torque and the potential energy of the dipole will respectively be: ?

Two metallic spheres of radii 1 cm and 3 cm are given charges of −1 × $10^{−2}$C and 5 × $10^{−2}$C, respectively. If these are connected by a conducting wire, the final charge on the bigger sphere is ?