Long Answer Typea) Two point charges Q1 = 400 
and Q2 = 100 
are kept fixed, 60 cm apart in vacuum.Find intensity of the electric field at midpoint of the line joining Q1 and Q2.
b) i) State Gauss' law.
ii) In an electric dipole, at which point is the electrical potential zero?
a) Obtain an expression for equivalent capacitance when three capacitors C1, C2 and C3 are connected in series.
b) A metallic wire has a resistance of 3.0 ohm and 0o Cand 4.8 ohm at 150o C. Find the temperature coefficient of resistance of its material?
a) Draw a labelled circuit diagram of a potentiometer to measure internal resistance of a cell. Write the working formula.
b) i) Define Curie temperature.
ii) If magnetic susceptibility of a certain magnetic material is 0.0001, find its relative permeability.
i) Labelled diagram of a potentiometer is shown below:
Internal resistance r of the cell is given by,
r = 
or r = R 
where, E is the potential difference between its poles.
and V is the potential difference between the ends of the resistance R.
b) i) Curie temperature: The temperature above which a ferromagnetic substance becomes paramagnetic substance is called the curie temperature of the substance. Te curie temperature of the iron is 770o C. It follows that at a temperature below 770o C, the iron is ferromagnetic and at a temperature above 770o C, the iron is paramagnetic.
ii) Given,
Magnetic susceptibility, 
Relative permeability, 
= 1 + 
= 1 + 0.0001
= 1.0001
Short Answer Typei) Two infinitely long current carrying conductors X and Y are kept parallel to each other, 24 cm apart in vacuum. They carry currents of 5 A and 7 A respectively, in the same direction, as shown in the figure below. Find the position os a neutral point, i.e., a point where resultant magnetic flux density is zero.
ii) If current through the conductor Y is reversed in direction, will neutral point lie between x and Y, to the left of X or to the left of Y?
i) Define Ampere in terms of force between two current carrying conductors.
ii) What is an ideal transformer.
Long Answer Typea) A coil having self-inductance of 0.7 H and resistance of 165 ohm is connected to an ac source of 275 V, 50 Hz. If 
.
Calculate:
i) reactance of the coil
ii) impedance of the coil
iii) current flowing through the coil
b) Draw a labelled graph showing variation of impedance of a series LCR circuit with frequency of the a.c. supply.
a) Derive Snell's law of refraction using Huygen's wave theory.
b) Monochromatic light of wavelength 650 nm falls normally on a slit of width 1.3 x 10-4 and the resulting Fraunhofer diffraction is obtained on a screen. Find the angular width of the central maxima.
a) In Young's Double Slit experiment, show that:
, where the terms have their usual meaning.
b) A ray of ordinary light is travelling in air. It is incident on air-glass pair at a polarising angle of 56o. Find the angle of refraction in glass.
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