Time allowed : 3 hours
Maximum Marks : 70

General Instructions :

(i) All questions are compulsory.
(ii) Marks for each question are indicated against it.
(iii) Question number 1 to 8 are very short-answer questions each of 1 mark. Answer them in about one sentence each.
(iv) Question number 9 to 18 are short-answer questions of 2 marks. Answer them in not more than 30 words each.
(v) Question number 19 to 27 are short-answer questions of 3 marks. Answer them in not more than 50 words each.
(vi) Question number 28 to 30 are long-answer questions of 5 marks each. Answer to these questions should be around 150 words each.
(vii) Use Log Tables, if necessary.

Q1) Draw an equipotential surface in a uniform electric field.  (Marks 1)

Q2) If a wire is stretched to double its original length without less of mass, how will the  resistivity of the wire be influenced?  (Marks 1)

Q3) Why do magnetic lines of force prefer to pass through iron than through air?  (Marks 1)

Q4) What is the power factor of an LCR series circuit at resonance? 
(Marks 1)

Q5) Why is the transmission of signals using ground waves restricted to frequencies upto 1500 kHz?  (Marks 1)

Q6) The polarising angle of a medium is 60^o. What is the refractive index of the medium?  (Marks 1)

Q7) How does the collector current change in a junction transistor, if the base region has larger width?  (Marks 1)

Q8) Two stars A and B have magnitudes -2 and +4 respectively. Which star appears brighter?  (Marks 1)

Q9) An electric flux of -6 x 10³ Nm²/C passes normally through a spherical Gaussian surface of radius 10 cm, due to a point charge placed at the center.
(i) What is the charge enclosed by the Gaussian surface?
(ii) If the radius of the Gaussian surface is doubled, how much flux would pass through the surface?  (Marks 2)

Q10) Three identical resistors, each of resistance R, when connected in series with a d.c. source, dissipate power X. If the resistors are connected in parallel to the same d.c. source, how much power will be dissipated? 
(Marks 2)

Q11) Define mutual inductance. State two factors on which the mutual inductance between a given pair of coils depends.  (Marks 2)

Q12) Light from a galaxy, having wavelength of 6000 A, is found to be shifted towards red by 50 A. Calculate the velocity of recession of the galaxy.  (Marks 2)

Q13) A converging lens has a focal length of 20 cm in air. It is made of a material of refractive index 1.6. If it is immersed in a liquid index 1.3, what will be its new focal length?  (Marks 2)

Q14) Draw a labelled ray diagram to show the image formation in astronomical telescope for normal adjustment position. Write down the equation for its magnifying power.  (Marks 2)

Q15) The half-life of a radioactive sample is 30 seconds. Calculates (i) the decay constant, and (ii) time taken for the sample to decay to 3/4th of its initial value.  (Marks 2)

Q16) Draw a logic circuit diagram showing how a NAND gate can be converted into a NOT gate.  (Marks 2)

Q17) What is an ideal diode? Draw the output waveform across R, for the input waveform given below :  (Marks 2)

Q18) Write, in brief, the method to determine the distance of an inferior planet from the sun.  (Marks 2)

Q19) Explain, with the help of a circuit diagram, the use of potentiometer for determination of internal resistance of a primary cell. Derive the necessary mathematical expression.  (Marks 3)

Q20) Calculate the resistance between A and B of the given network.  (Marks 3)

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