PART I (Compulsory)
1. Answer all questions briefly and to the point: [20]
(i) Define 'electric potential' at a point in an electric field.
(ii) A capacitor is charged through a potential difference of 200 V when 0.1 C charge is stored in it. How much energy will it release when it is discharged?
(iii) Find out the resistivity of a conductor in which a current density 2.5 A/m2 is found to exist when an electric field 15 V/m is applied on it.
Fig 1
(iv) Find out the magnitude of resistance X in the given circuit diagram (Fig 1) when no current flows through the 5 ohm resistor.

(v) Define magnetic 'permeability'.
(vi) Write an expression for the magnetic field produced by an infinitely long straight wire carrying a current i, at a short perpendicular distance'a' from itself.
(vii) A bar magnet placed in a uniform magnetic field  of strength 0.3 T, with its axis at 30 degree to the field, experiences a torque of 0.06 Nm. What is the magnetic moment of the bar magnet?
(viii) With reference to alternating currents and voltages, state any one fundamental difference between 'resistance' and 'reactance'.
(ix) Define the term 'coherence' for light waves.
(x) A plane diffraction grating is used with a monochromatic source of wavelength 5000 A under normal incidence. The second order maximum is obtained at a diffraction angle of 30 degree. Find the grating element.
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ICSE Physics SAmple Paper

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