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Model Sample Paper -3

Q.1. What is the significance of negative energy of an electron?

Q.2. Why do we prefer phosphor -bronze alloy for the suspension wire of a moving coil galvanometer?

Q.3. If the earth did not have an atmosphere would its average surface temperature be higher or lower than what it is now?

Q.4. What is the relevance of large value of dielectric constant, K (= 81) for water?

Q.5. Why alternating current measuring instruments have a nonlinear scale?

Q.6. What type of feed back is required in an oscillator?

Q.7. Why should the element of a heater get red hot while the cable carrying current remains cold?

Q.8. What is logic gate?

Q.9. When a current of 0.5 A passed though two resistances in series, the potential difference between the ends of the series arrangement is 12.5 V. On connecting them in parallel and passing the current of 1.5 A, the potential difference between their ends is 6 V, calculate the two resistances.

Q.10. Prove the relation {A + d = i + e} for a prism, where the symbols have their usual meanings.

Q.11. A solution of chrome - alum is poured in a watch glass placed over two nearby (- 1mm apart) pole pieces of a magnet. Draw and explain the shape of liquid. What happens if pole pieces are moved apart?

Q.12. Why is 92238U not suitable for nuclear fission ?

Q.13. A cube of side b has a charge q at each of its vertices. Determine the potential and electric field due to this charge array at the center of cube.

Q.14. Permanent magnets are made of steel while the core of transformer is made of soft iron. Why?

Q.15.What are two types of rainbow? How are they obtained? Draw the ray diagram.

Q.16.How can you determine the internal resistance of a cell graphically using a potentiometer?

Q.17.Calculate the energy liberated when a single helium nucleus is formed by the fusion of two deuterium nuclei. Give mass of 1H2 = 2.01478 a.m.u. mass of 2He4 = 4.00388 a.m.u.

Q.18.A rectangular loop is inside a uniform magnetic field as shown in the figure. What is induced e.m.f. ? What is induced e.m.f. if the coil enters in to, or moves away from the region of magnetic field?

Q.19.Deduce laws of refraction on the basis of Huygen's principle.

Q.20.Derive an expression for current though a semiconductor in terms of concentration and mobility of intrinsic carriers. Hence obtain an expression for electrical resistivity of a semiconductor.

Q.21.Derive a relation between internal resistance, e.m.f. and terminal potential difference for a cell.

Q.22.Derive formula for calculation of surface temperature of the sum.

Q.23.With the help of a circuit diagram explain how using a silver voltammeter can test the accuracy of an ammeter.

Q.24.The dispersive power of crown and flint glasses are 0.2 and 0.4 respectively. A lens of crown glass and that of flint glass are combined to form an achromatic doublet of focal length 20-cm. What is the focal length of the lenses and equivalent total length of the combination?

Q.25.The electric field of a plane electromagnetic wave in vacuum is represented by

(i) What is. the direction of propagation of the electromagnetic waves?

(ii) Determine the wavelength of the wave.

(iii) Compute the component of associated magnetic field.

Q.26. In the circuit in the figure below, the value ofb =100, find IB, VBE VCE and VBC when IC = 1.5 mA.


Q.27. A chamber is maintained at a uniform magnetic field of 5 x 1 0-3 T. An electron with a speed 101 m/s enters the chamber in a direction normal to the field. Calculate (i) radius of path (ii) frequency of revolution of the electron.

Q.28. Prove that average power consumed in an a.c. circuit is given by

How the power factor of circuit varies as frequency of applied a.c. is varied OR

An inductor and a resistor are connected in series across a d.c. Obtain an expression for the growth of current. The battery is disconnected after some time. Obtain an expression for the decay of current.

Q.29. A spherical conductor of radius 18 cm is charged positively with 8 x 10-9 C and then connected with another sphere of radius 9 cm carrying a negative charge of 4 x10-9 C. Calculate (a) Potential of each sphere before and after contact (b) Charge on each sphere after contact.

Q.30. (a) Ultraviolet light of wavelength 2271 A from a 100 W mercury source irradiates a photo cell made of molybdenum metal. If the stopping potential is - 1 3 V, estimate the work function of the metal.

(b) How would the photocell respond to high intensity (105 Wm-1) red light of wavelength 6328 Ao?