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PHY PRACTICE PAPER 1 DERIVATION 1) Derive the principle of wheatstone bridge using Kirchoff s law. b)How does the balancing point of a Wheatstone bridge get affected when the i) Position of cell and Galvanometer are interchanged? ii) Position of the known and unknown resistances is interchanged? c) Plot a graph showing the variation of conductivity with the temperature T in a metallic conductor. 2) A coil of inductance L , a capacitor of capacitance C , & a resistor of resistance R are all put in series with an alternating source of emf E = E0 sin t. Derive expression for i) Total impedance of circuit, and ii) Frequency of source emf for which circuit will show resonance. b) The peak value of an AC is 5A and its frequency is 60Hz. Find its rms value. How long will the current take to reach the peak value starting from zero? 3) a)Derive an expression for the energy stored in a parallel plate capacitor with air between the plates. b)How does the stored energy change if air is replaced by a medium of dielectric constant k ? c) A parallel-plate capacitor is charged to a potential difference V by a dc source. The capacitor is then disconnected from the source. If the distance between the plates is doubled, state with reason how the following change (i) Electric field between the plates (ii) Capacitance, and (iii) Energy stored in the capacitor 4) 1) Draw a ray diagram of a compound microscope and explain its working. Write an expression for the total magnification when the final image is formed at the near point. 5) 1) Find an expression for force per unit length between two parallel current carrying conductors. Define Ampere from the formula. 2) Two parallel wires of 9m each are separated by a distance of 0.15m. If they carry equal currents in the same direction and exert a total force of 30 10 7 on each other, then find the value of current 6) 1) Describe the principle, construction and working of a moving coil galvanometer . 7) a. Use Gauss law to derive the expression for the electric field due to a straight uniformly charged infinite line of charge density C/m. b. Draw a graph to show the variation of E with perpendicular distance r from the line of charge. 8) Draw the schematic arrangement for winding of primary and secondary coils in a transformer when the two coils are wound on top of each other. b. state the underlying principle of a step-up transformer and obtain the expression for the ratio of secondary to primary voltage in terms of number of turns.
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