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Model Sample Paper - 6

Q.1. Name two physical conditions on which the resistivity of a metal depends.

Q.2.Why does the picture on a TV screen become distorted when a magnet is brought near the screen?

Q.3.Does a beam of white light give a spectrum on passing through a hollow prism?

Q.4.Why do we prefer a choke to a rheostat in controlling current in a.c. circuit?

Q.5.The standard resistance coils are made of manganin. Why ?

Q.6.When light undergoes reflection what happens to (a) frequency (b) wavelength of light ?

Q.7.There are certain types of stars called variable stars which undergo periodic change in their light output. If such a star doubles its light output, how much does its magnitude change?

Q.8.What is the reactance of an inductor in a D.C. circuit?

Q.9.State Hubble's law. What is the significance of Hubble's constant?

Q.10.An applied voltage signal consists of a superposition of a D.C. voltage and an a.c. voltage of high frequency. The circuit consists of an inductor and a capacitor in series. Show that D.C. signal will appear across C and the a.c signal across L.

Q.11.A loop of irregular shape is made of a flexible wire and placed in an external field. What shape the loop acquires when a current is passed though it? Explain.

Q.12.State the conditions which must be satisfied for two light sources to be coherent.

Q.13.Long distance radio broadcasts use short wave bands, why?

Q.14.A ray of light falls normally on one face of a prism of angle 450. If critical angle for materiel of prism is 450, trace the course of rays. Calculate m ?

Q.15.An object of size 3 cm is placed 14 cm in front of a concave lens of focal length 21 cm. Describe the image produced by the lens. What happens of the object is moved farther from the lens?

Q.16. State Coulomb's law of magnetostatics. What is the constant of proportionality in S.I. units and give its value.

Q.17. Obtain the binding energy of the nucleus, 26Fe56 in units of MeV from the following data mH = 1.007825 a.m.u. mn = 1.0086659 a.m.u. m[26Fe56] = 55.934939 a.m.u., 1amu = 931.5 MeV.

Q.18. In a transistor, base is made thin and doped with little impurity atoms. Why?

Q.19. Explain through a labelled circuit diagram the working of p-n-p transistor as common base amplifier.

Q.20. An electron moves a distance of 6 cm when accelerated through from rest by an electric field of strength of 2 x 104 N/C. Calculate the time of travel. Given mass of electron 9 1 X 10-31 kg.

Q.21. If a current of 2 A be passed through a copper voltammeter for 2 hours the amount of copper deposited is 4.5 g. Calculate electrochemical equivalent of nickel when the atomic weights of copper and nickel are 63.5 and 58.7 respectively.

Q.22. Derive an expression for resistivity of the material of a given conductor in terms of relaxation time.

Q.23. Discuss the important properties of nuclear forces.

Q.24. Discuss communication of T.Y. video signals of high frequency using high T.V. tower. Deduce an expression for the maximum area over which a signal can be sent on earth by ground wave if an antenna of height h is used to transmit the signal.

Q.25. In the following figures which of the diodes are forward biased and which are reverse biased?

Q.26.A galvanometer has a resistance of 50 ohms and gives full-scale deflection with a current of 50 mA. Calculate resistance required to measure 10 Ampere current.

Q.27.A long wire is best as shown in figure. What will be magnitude and direction of magnetic field at the center O if a current of 2 A is passed through the wire? Radius of circular path is lm and the straight wire does not touch circular loop.

Q.28. Calculate electric field due to a dipole at a point on its axis and at a distance d from its centre. OR A loop of wire of negligible thickness has a radius r and charge q is uniformly distributed over the loop. Find the electric field E at a point P situated at a distance x from its center.

Q.29. Describe Millikan's method for determination of electronic change on electron.

Q.30.A 25 0 m F capacitor, a 0.1 0 henry inductor and a 25.0 ohm resistor are connected in series with an a.c. source whose e.m.f is given by E = 310 sin 314t. (i) What is the frequency of the e.m.f.?(ii) Calculate

(a) the reactance of the circuit (b) the impedance of the circuit (c) Current in the circuit.

Figs Q25&28