# Aug 13, 2014 2:06 pm1) Two point electric charges of unknown magnitude and sign are placedat a distance 'd' apart. The electric field intensity is zero at apoint not b/w the charges but on the line joining them. Write the eesential condition (s) for this and estimate the position of this point.2) (a)plot a graph to show the variation of magnetic field with dist. from the axis of a current carrying conductor of radius 'a'(b) A converging lens has a focal length of 20cm in air. It is made of a material of refractive index 1.5. If it is immersed in water of refractive index 4/3, wh at will be the new focal length?3) A cell of emf (ξ) and internal resistance (r) is connected across a variable external resistance (R). Plot graph to show variation of (i) ξ with R (ii) Terminal p.d of the cell (V) with Resistance(R).4)(a)Two resistance filament s of same length are connected first in series and then in parallel. Find the ratio of power dissipated in both cases assuming that equal current flows in the main circuit.(b)Twenty seven drops of same size are charge d at 220V each. They coales c e to from a bigger drop. Calculate the pot ential of the bigger drop.5)(a)A wire of unifor m cross - section ’A’ and length ‘ ? ’ has a resistance of 16Ω. It is cut into four equal parts. Each part is stretched uniformly to length ? and all the four stretched parts are connected in parallel. Find the total r esis tance of the combination so formed. Assume that stretching of wires do es not cause any change in the density of its material.(b) A bar magnet M is dropped so that it falls vertically through Page 3 of 6 the coil C. The graph obtained for voltage produced across the coil vs. time is as shown in the figure     (i) Explain the shape of the graph (ii) Why is negative peak longer than the positive peak?6)(a)A proton and an alpha par ticle of the same velocity enter in turn a region of uniform magnetic field, acting perpendicular to their direction of moti on. Deduce the ratio of the radi i of the circular paths described by the particles.(b)A jet plane is travelling west at 450ms - 1 .If the horizontal component of earth’s magnetic field at that place is 4x10 - 4 T and the angle of dip is 30 0 , find the emf induced between the ends of wings having a span of 30m.

### Answered by Romal Bhansali | 17th Aug, 2014, 01:46: PM

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